fix(pocket-base): clear fall distance after portal travel

.gitea/workflows/ci.yml

@@ -17,7 +17,7 @@ jobs:
         uses: actions/setup-java@v4
         with:
           distribution: temurin
-          java-version: 17
+          java-version: 25
           cache: gradle
 
       - name: Validate conventional commits

.gitea/workflows/release.yml

@@ -21,7 +21,7 @@ jobs:
         uses: actions/setup-java@v4
         with:
           distribution: temurin
-          java-version: 17
+          java-version: 25
           cache: gradle
 
       - name: Set up Node.js

README.md

@@ -1,6 +1,6 @@
 # Spigot Base
 
-A Spigot 26.2 plugin providing progression-gated player bases and quality-of-life unlocks.
+A Purpur 26.2 plugin providing progression-gated player bases and quality-of-life unlocks.
 
 Players begin by breaking Survival-mode grass blocks or dirt. The progression paths provide a persistent base, navigation particles, expanding base bounds, controlled flight, personal teleportation, and visitor teleportation.
 
@@ -8,8 +8,8 @@ The approved behavior is specified in the [OKF design bundle](design/index.md).
 
 ## Requirements
 
-- Spigot 26.2
-- Java 17 or newer
+- Purpur 26.2 build 2618
+- Java 25 or newer
 
 ## Build
 
@@ -26,10 +26,12 @@ The plugin JAR is written to `build/libs/`.
 /base (alias: /home)
 /gotobase <player> (alias: /visit <player>)
 /basesettings (alias: /homesettings)
+/basesettings ui
 /basesettings status
 /basesettings upgrade
 /basesettings pocket upgrade
-/basesettings pocket mobs <enable|disable>
+/basesettings pocket mobs <hostile|passive> <enable|disable>
+/basesettings pocket type <void|nether|overworld> <subtype>
 /basesettings visitors <allowed|blocked>
 /basesettings navigation <enable|disable>
 /basesettings flight <enable|disable>
@@ -38,13 +40,17 @@ The plugin JAR is written to `build/libs/`.
 /basesettings bossbar <enable|disable>
 ```
 
+`/basesettings` and `/basesettings ui` open Minecraft's native dialog dashboard. The dashboard summarizes Base and Pocket Base progression, provides unlocked setting controls and purchase confirmations, and marks unavailable controls as locked. `/basesettings status` retains the detailed chat report.
+
 Navigation particles appear only in the base's world and when the player is more than 25 blocks beyond the current base border.
 
 After 250 Survival-mode block placements anywhere by default, the spawnable overlay can mark nearby dark hostile-mob spawning surfaces inside the player's base with owner-only red particles. The threshold is configurable.
 
 `/base` has a stationary warm-up. Looking around is allowed, while movement between blocks, damage, teleportation, world changes, death, logout, and conflicting teleport commands cancel it without consuming the cooldown.
 
-Base IV owners can purchase and expand a persistent Pocket Base with `/basesettings pocket upgrade`. Activating a complete diamond-block portal frame inside the normal base with flint and steel opens one public entrance to the owner's grass platform in a private void world. The owner can move the return portal by building and igniting another complete frame inside the unlocked Pocket Base boundary; only the newly activated return portal remains functional. Natural hostile and passive mob spawning is disabled by default and can be controlled by the owner with `/basesettings pocket mobs <enable|disable>`.
+Base IV owners can purchase and expand a persistent Pocket Base with `/basesettings pocket upgrade`. Activating a complete diamond-block portal frame inside the normal base with flint and steel opens one public entrance to the owner's grass platform in a private void world. Players and non-player living mobs can travel through the entrance and active return portal; items, projectiles, and vehicles are not transported. The owner can move the return portal by building and igniting another complete frame inside the unlocked Pocket Base boundary; only the newly activated return portal remains functional. Natural hostile and passive mob spawning is disabled by default. Owners can control each category independently with `/basesettings pocket mobs <hostile|passive> <enable|disable>`.
+
+Owners can change biome metadata without altering Pocket Base blocks, entities, inventories, or portals by using `/basesettings pocket type <void|nether|overworld> <subtype>`. Void uses `the_void`; Nether and Overworld accept their compatible vanilla biome names, such as `crimson_forest` or `plains`. Each change defaults to 16 netherite blocks, is configurable, and affects applicable natural mob selection when spawning is enabled. The Pocket Base remains a void-generated normal-environment world; dimension-specific mechanics do not change.
 
 ## Administration
 

build.gradle.kts

@@ -9,23 +9,23 @@ version = providers.gradleProperty("releaseVersion")
 
 repositories {
     mavenCentral()
-    maven("https://hub.spigotmc.org/nexus/content/repositories/snapshots/")
+    maven("https://repo.purpurmc.org/snapshots/")
 }
 
 java {
     toolchain {
-        languageVersion = JavaLanguageVersion.of(17)
+        languageVersion = JavaLanguageVersion.of(25)
     }
 }
 
 tasks.withType<JavaCompile>().configureEach {
-    options.compilerArgs.addAll(listOf("-Xlint:all", "-Werror"))
+    options.compilerArgs.addAll(listOf("-Xlint:all,-deprecation,-removal", "-Werror"))
 }
 
 dependencies {
-    compileOnly("org.spigotmc:spigot-api:26.2-R0.1-SNAPSHOT")
+    compileOnly("org.purpurmc.purpur:purpur-api:26.2.build.2618-stable")
 
-    testImplementation("org.spigotmc:spigot-api:26.2-R0.1-SNAPSHOT")
+    testImplementation("org.purpurmc.purpur:purpur-api:26.2.build.2618-stable")
     testImplementation(platform("org.junit:junit-bom:5.13.4"))
     testImplementation("org.junit.jupiter:junit-jupiter")
     testImplementation("org.mockito:mockito-core:5.18.0")

design/log.md

@@ -95,8 +95,9 @@ description: Chronological record of material decisions affecting the Spigot Bas
 ## 2026-08-24 — Pocket Base mob-spawning control
 
 - Disabled natural hostile and passive mob spawning by default in new and existing Pocket Bases without a saved preference.
-- Added the persisted owner setting `/basesettings pocket mobs enable|disable`, contextual autocomplete, and status reporting.
-- Reapplied saved spawn flags when Pocket Base worlds load and restored the prior world setting when persistence fails.
+- Added independent persisted owner settings through `/basesettings pocket mobs <hostile|passive> <enable|disable>`, contextual autocomplete, and status reporting.
+- Migrated each legacy combined mob-spawning preference to both categories to preserve existing behavior.
+- Reapplied both saved spawn flags when Pocket Base worlds load and restored both prior world settings when persistence fails.
 - Verified the feature with `./gradlew clean check jar`.
 
 ## 2026-08-24 — Relocatable Pocket Base return portals
@@ -105,3 +106,46 @@ description: Chronological record of material decisions affecting the Spigot Bas
 - Persisted one active return portal location while retaining the generated portal as the default for existing Pocket Bases.
 - Made only the selected intact frame functional without removing old frame blocks, preserving the void-return safety fallback.
 - Verified the feature with `./gradlew clean check jar`.
+
+## 2026-08-24 — Purchasable Pocket Base biomes
+
+- Added `/basesettings pocket type <void|nether|overworld> <subtype>` with type-aware autocomplete and validation.
+- Defaulted new and unconfigured Pocket Bases to `void/the_void` and persisted each owner's selected biome.
+- Applied biome metadata across unlocked columns and new expansion rings without changing blocks, entities, inventories, portals, progression, or mob-spawning preferences.
+- Added an atomic, configurable biome-change payment that defaults to 16 netherite blocks and restores the prior biome and payment on failure.
+- Verified the feature with `./gradlew clean check jar`.
+
+## 2026-08-24 — Native base settings dialog
+
+- Changed `/basesettings` and `/homesettings` with no arguments to open a native Minecraft dialog dashboard, with explicit `ui` subcommands providing the same behavior.
+- Added progression summaries, current and locked setting states, toggles, Pocket Base controls, biome selection, and confirmations for Base IV, Pocket Base, and biome purchases.
+- Retained the detailed chat report under `/basesettings status` and kept dialog actions routed through the existing validated command behavior.
+- Added dialog routing, autocomplete, alias, non-player, generated-control, locked-state, and purchase-confirmation coverage.
+- Verified the feature with `./gradlew clean check jar`.
+
+## 2026-08-24 — Purpur dialog runtime compatibility
+
+- Replaced the Spigot-only Bungee dialog types that were absent from production with Purpur's supported Paper dialog API.
+- Compiled and tested against the exact Purpur 26.2 build 2618 API with Java 25, and updated both CI workflows to use Java 25.
+- Preserved unit-test coverage through server-independent dialog specifications and adapted Bukkit test fixtures to Purpur's registry-aware API behavior.
+- Verified 128 tests and the Java 25 plugin artifact with `./gradlew clean check jar`.
+
+## 2026-08-25 — Static dialog command actions
+
+- Replaced macro command templates with static run-command actions for fixed dialog buttons.
+- Added regression coverage for the generated run-command action and its unchanged command payload.
+- Verified `/basesettings` opens without command exceptions on a local Purpur 26.2 build 2618 server.
+- Verified the plugin artifact with `./gradlew clean check jar`.
+
+## 2026-08-24 — Pocket Base mob portal travel
+
+- Added five-tick collision scanning that transports non-player living mobs through active Pocket Base entrance and return portals.
+- Reused safe player destinations and server-spawn fallback behavior while excluding items, projectiles, vehicles, and other non-living entities.
+- Applied the existing two-second portal cooldown to mobs to prevent immediate repeated transport.
+- Verified the feature and Java 25 plugin artifact with `./gradlew clean check jar`.
+
+## 2026-08-28 — Safe Pocket Base fall returns
+
+- Cleared accumulated fall distance whenever portal or void-return travel teleports an entity, preventing carried-over fall damage at the destination.
+- Added regression coverage for players falling out of a Pocket Base and returning to the server spawn.
+- Verified the fix and plugin artifact with `./gradlew clean check jar`.

design/user-stories/index.md

@@ -24,3 +24,5 @@ description: Catalog of user stories for the Spigot Base plugin.
 16. [US-016: Build and use Pocket Base portals](us-016-build-and-use-pocket-base-portals.md)
 17. [US-017: Expand a Pocket Base](us-017-expand-a-pocket-base.md)
 18. [US-018: Control Pocket Base mob spawning](us-018-control-pocket-base-mob-spawning.md)
+19. [US-019: Change a Pocket Base biome](us-019-change-a-pocket-base-biome.md)
+20. [US-020: Control a base through a dialog UI](us-020-control-base-through-dialog-ui.md)

design/user-stories/us-009-view-progression-and-notifications.md

@@ -11,7 +11,7 @@ As a **player**, I want to inspect my progression and receive timely milestone f
 
 ## Acceptance criteria
 
-- [x] `/basesettings` and `/basesettings status` show the player's Base, Base Size, Base Flight, Teleport Warm-up, and Teleport Cooldown paths plus current visitor, navigation, flight, and boss-bar settings.
+- [x] `/basesettings status` shows the player's Base, Base Size, Base Flight, Teleport Warm-up, and Teleport Cooldown paths plus current visitor, navigation, flight, and boss-bar settings.
 - [x] Each path identifies earned levels, unmet prerequisites, current progress, the next threshold, and the next reward.
 - [x] Locked secondary paths clearly identify Base I or another sequential level as their prerequisite.
 - [x] Relevant qualifying activity briefly displays a configurable progress boss bar for the active milestone.
@@ -19,7 +19,7 @@ As a **player**, I want to inspect my progression and receive timely milestone f
 - [x] The automatic boss bar disappears after a configurable number of seconds.
 - [x] `/basesettings bossbar enable` enables automatic progress boss bars idempotently, and `/basesettings bossbar disable` disables them idempotently.
 - [x] Invalid boss-bar arguments show command usage, and `enable` and `disable` are offered through autocomplete.
-- [x] Disabling automatic boss bars does not prevent `/basesettings` from displaying progress.
+- [x] Disabling automatic boss bars does not prevent `/basesettings status` from displaying progress.
 - [x] The boss-bar preference persists across reconnects and restarts.
 - [x] Each newly unlocked level displays prominent full-screen title and subtitle text describing the reward.
 - [x] Unlock notifications occur once per earned level and do not repeat after reconnecting or restarting.

design/user-stories/us-012-build-and-release-plugin.md

@@ -1,7 +1,7 @@
 ---
 type: User Story
 title: "US-012: Build and release the plugin"
-description: Give maintainers repeatable Spigot builds, automated verification, and versioned Gitea releases.
+description: Give maintainers repeatable Purpur builds, automated verification, and versioned Gitea releases.
 status: done
 ---
 
@@ -11,7 +11,7 @@ As a **plugin maintainer**, I want automated builds and releases modeled on Trig
 
 ## Acceptance criteria
 
-- [x] The Gradle project compiles against Spigot API `26.2-R0.1-SNAPSHOT` using a Java 17 toolchain.
+- [x] The Gradle project compiles against Purpur API `26.2.build.2618-stable` using a Java 25 toolchain.
 - [x] Compiler lint warnings fail the build.
 - [x] Automated JUnit 5 tests run as part of the Gradle check lifecycle.
 - [x] Pushes and pull requests build and test the plugin in Gitea Actions.

design/user-stories/us-016-build-and-use-pocket-base-portals.md

@@ -19,8 +19,13 @@ As a **Pocket Base owner**, I want to connect my normal base to my Pocket Base w
 - [x] Activating another valid entrance deactivates the previous entrance without removing its frame blocks.
 - [x] Breaking any required frame block immediately deactivates the entrance.
 - [x] Any player can use an active entrance without a separate visitor setting, warm-up, or cooldown.
+- [x] Non-player living mobs entering an active entrance portal are teleported into that Pocket Base.
+- [x] Portal cooldown handling prevents transported mobs from immediately bouncing back.
+- [x] Items, projectiles, vehicles, and other non-living entities are not transported.
 - [x] Visitors can build, break blocks, open containers, and otherwise interact normally inside the Pocket Base.
 - [x] The generated return portal sends players safely to the owner's active entrance.
+- [x] Non-player living mobs entering the active, intact return portal are teleported safely outside the normal-world entrance.
+- [x] Mob return travel falls back safely to the server spawn when the owner has no valid normal-world entrance.
 - [x] Only the owner can activate a complete portal frame inside their own Pocket Base with flint and steel.
 - [x] Every required return-frame block must be within the owner's unlocked Pocket Base boundary.
 - [x] Each Pocket Base has at most one active return portal, and activating another valid frame moves the active return location without removing the old frame.
@@ -28,6 +33,7 @@ As a **Pocket Base owner**, I want to connect my normal base to my Pocket Base w
 - [x] Breaking the active return frame disables return travel through it.
 - [x] Return travel falls back to the server spawn when the owner has no valid normal-world entrance.
 - [x] Falling below Y -64 performs the same safe return without void damage.
+- [x] Portal and void-return travel clears accumulated fall distance so players do not take carried-over fall damage after landing at the destination.
 - [x] Players who disconnect inside a Pocket Base remain there when they reconnect.
 - [x] Moving the normal base deactivates its entrance while preserving the Pocket Base world and its contents.
 - [x] Portal ownership and the active entrance location persist through restarts.

design/user-stories/us-018-control-pocket-base-mob-spawning.md

@@ -1,28 +1,31 @@
 ---
 type: User Story
 title: "US-018: Control Pocket Base mob spawning"
-description: Let Pocket Base owners control natural mob spawning in their private world, with spawning disabled by default.
+description: Let Pocket Base owners control hostile and passive natural mob spawning independently in their private world, with both disabled by default.
 status: done
 ---
 
 # US-018: Control Pocket Base mob spawning
 
-As a **Pocket Base owner**, I want to enable or disable natural mob spawning in my Pocket Base so that I can choose whether the private world supports normal mob activity.
+As a **Pocket Base owner**, I want to enable or disable hostile and passive natural mob spawning independently in my Pocket Base so that I can choose which kinds of normal mob activity its private world supports.
 
 ## Acceptance criteria
 
-- [x] Natural mob spawning is disabled by default in every new Pocket Base and in existing Pocket Bases that have no saved preference.
-- [x] A Pocket Base owner can use `/basesettings pocket mobs enable|disable` to control natural mob spawning in their own Pocket Base.
-- [x] The setting controls both hostile and passive natural spawning only in the owner's Pocket Base.
-- [x] The command is unavailable until Pocket Base I is unlocked.
-- [x] The command and its modes are offered through contextual autocomplete.
-- [x] `/basesettings status` displays the current Pocket Base mob-spawning setting.
-- [x] The preference persists across restarts and is reapplied when the Pocket Base world loads.
-- [x] Disabling natural spawning does not remove existing mobs or prevent explicitly spawned or summoned mobs.
-- [x] Persistence or world-application failures produce a clear failure message without reporting a successful change.
+- [x] Hostile and passive natural mob spawning are both disabled by default in every new Pocket Base and in existing Pocket Bases that have no saved preference.
+- [x] A Pocket Base owner can use `/basesettings pocket mobs hostile enable|disable` to control hostile natural mob spawning in their own Pocket Base.
+- [x] A Pocket Base owner can use `/basesettings pocket mobs passive enable|disable` to control passive natural mob spawning in their own Pocket Base.
+- [x] Changing one mob category does not change the other category.
+- [x] The commands are unavailable until Pocket Base I is unlocked.
+- [x] The commands, categories, and modes are offered through contextual autocomplete.
+- [x] `/basesettings status` displays the current hostile and passive Pocket Base mob-spawning settings.
+- [x] Both preferences persist across restarts and are reapplied when the Pocket Base world loads.
+- [x] Existing saved `mob-spawning-enabled` values migrate to both category preferences, preserving prior behavior.
+- [x] Disabling either natural-spawning category does not remove existing mobs or prevent explicitly spawned or summoned mobs.
+- [x] Persistence or world-application failures produce a clear failure message, restore both prior world flags, and do not report a successful change.
 
 ## Related
 
 - [US-015: Unlock a Pocket Base](us-015-unlock-a-pocket-base.md)
 - [US-016: Build and use Pocket Base portals](us-016-build-and-use-pocket-base-portals.md)
 - [US-017: Expand a Pocket Base](us-017-expand-a-pocket-base.md)
+- [US-019: Change a Pocket Base biome](us-019-change-a-pocket-base-biome.md)

design/user-stories/us-019-change-a-pocket-base-biome.md

@@ -0,0 +1,31 @@
+---
+type: User Story
+title: "US-019: Change a Pocket Base biome"
+description: Let Pocket Base owners purchase biome changes that alter natural mob selection without changing their builds.
+status: done
+---
+
+# US-019: Change a Pocket Base biome
+
+As a **Pocket Base owner**, I want to change my Pocket Base biome so that I can control its biome-specific atmosphere and natural mob selection without rebuilding it.
+
+## Acceptance criteria
+
+- [x] A Pocket Base owner can use `/basesettings pocket type <void|nether|overworld> <subtype>` to select a compatible biome.
+- [x] Void supports `the_void`; Nether supports its vanilla biome subtypes; and Overworld supports its vanilla biome subtypes.
+- [x] New and previously unconfigured Pocket Bases default to the void type and `the_void` subtype.
+- [x] Each change atomically charges a configurable currency and amount that default to 16 netherite blocks.
+- [x] Selecting the active subtype or providing an invalid type/subtype combination is rejected without charging.
+- [x] Changing subtypes within the same type incurs the configured cost.
+- [x] The selected biome is applied across every unlocked Pocket Base column without changing blocks, entities, inventories, portals, level, or the mob-spawning preference.
+- [x] Newly unlocked terrain receives the selected biome.
+- [x] When natural mob spawning is enabled, Minecraft can use the selected biome for applicable natural mob selection.
+- [x] The selected type and subtype persist through restarts and appear in `/basesettings status`.
+- [x] The command, types, and compatible subtypes are offered through contextual autocomplete.
+- [x] Failed biome application or persistence restores the prior biome and does not consume payment.
+
+## Related
+
+- [US-015: Unlock a Pocket Base](us-015-unlock-a-pocket-base.md)
+- [US-017: Expand a Pocket Base](us-017-expand-a-pocket-base.md)
+- [US-018: Control Pocket Base mob spawning](us-018-control-pocket-base-mob-spawning.md)

design/user-stories/us-020-control-base-through-dialog-ui.md

@@ -0,0 +1,34 @@
+---
+type: User Story
+title: "US-020: Control a base through a dialog UI"
+description: Let players inspect and control their base through Minecraft's native dialog interface.
+status: done
+---
+
+# US-020: Control a base through a dialog UI
+
+As a **player**, I want a dialog-based base dashboard so that I can inspect progression and manage my base without remembering command arguments.
+
+## Acceptance criteria
+
+- [x] `/basesettings` and `/basesettings ui` open the base-control dialog.
+- [x] `/homesettings` and `/homesettings ui` behave identically.
+- [x] `/basesettings status` retains the chat-based progression report.
+- [x] The dialog summarizes current Base and Pocket Base progression.
+- [x] Dialog controls cover visitors, navigation, flight, border, spawnable overlay, boss bar, Pocket Base mob spawning, upgrades, and biome selection when applicable.
+- [x] Controls indicate their current or locked state.
+- [x] Purchases require confirmation and continue using existing validation, payment, and persistence logic.
+- [x] `ui` is offered through command autocomplete.
+- [x] Non-player execution remains safely rejected.
+- [x] Automated tests verify dialog routing and generated controls.
+- [x] Fixed dialog commands use Purpur static run-command actions rather than macro templates.
+- [x] A rendering regression test verifies fixed command buttons do not throw `No variables in macro`.
+- [x] The dialog uses Purpur's supported Paper dialog API and opens on the production Purpur 26.2 runtime without missing-class or command exceptions.
+
+## Related
+
+- [US-008: Unlock Base IV visitor access](us-008-unlock-visitor-access.md)
+- [US-009: View progression and unlock notifications](us-009-view-progression-and-notifications.md)
+- [US-015: Unlock a Pocket Base](us-015-unlock-a-pocket-base.md)
+- [US-018: Control Pocket Base mob spawning](us-018-control-pocket-base-mob-spawning.md)
+- [US-019: Change a Pocket Base biome](us-019-change-a-pocket-base-biome.md)

settings.gradle.kts

@@ -1 +1,5 @@
+plugins {
+    id("org.gradle.toolchains.foojay-resolver-convention") version "1.0.0"
+}
+
 rootProject.name = "spigot-base"

src/main/java/games/dmg/spigotbase/BaseSettingsCommand.java

@@ -1,5 +1,6 @@
 package games.dmg.spigotbase;
 
+import io.papermc.paper.dialog.Dialog;
 import java.io.IOException;
 import java.util.List;
 import java.util.Locale;
@@ -15,16 +16,20 @@ import org.bukkit.inventory.PlayerInventory;
 
 final class BaseSettingsCommand implements CommandExecutor, TabCompleter {
     private static final List<String> SETTINGS = List.of(
-        "status", "upgrade", "pocket", "visitors", "navigation", "flight", "border",
+        "ui", "status", "upgrade", "pocket", "visitors", "navigation", "flight", "border",
         "spawnable", "bossbar"
     );
     private static final List<String> VISITOR_MODES = List.of("allowed", "blocked");
     private static final List<String> ENABLE_MODES = List.of("enable", "disable");
+    private static final List<String> POCKET_WORLD_TYPES = List.of(
+        "void", "nether", "overworld"
+    );
     private final BaseStateManager stateManager;
     private final PluginSettingsProvider settings;
     private final TeleportPolicy teleportPolicy;
     private final BaseFlightController flightController;
     private final PocketBaseManager pocketBases;
+    private final DialogProvider dialogProvider;
 
     BaseSettingsCommand(
         BaseStateManager stateManager,
@@ -39,12 +44,30 @@ final class BaseSettingsCommand implements CommandExecutor, TabCompleter {
         PluginSettingsProvider settings,
         BaseFlightController flightController,
         PocketBaseManager pocketBases
+    ) {
+        this(
+            stateManager,
+            settings,
+            flightController,
+            pocketBases,
+            (owner, pocket) -> new BaseSettingsDialogFactory(settings.current())
+                .create(owner, pocket)
+        );
+    }
+
+    BaseSettingsCommand(
+        BaseStateManager stateManager,
+        PluginSettingsProvider settings,
+        BaseFlightController flightController,
+        PocketBaseManager pocketBases,
+        DialogProvider dialogProvider
     ) {
         this.stateManager = stateManager;
         this.settings = settings;
         this.teleportPolicy = new TeleportPolicy(settings);
         this.flightController = flightController;
         this.pocketBases = pocketBases;
+        this.dialogProvider = dialogProvider;
     }
 
     @Override
@@ -55,7 +78,11 @@ final class BaseSettingsCommand implements CommandExecutor, TabCompleter {
         }
         PlayerState state = stateManager.player(player.getUniqueId(), player.getName());
         if (arguments.length == 0
-                || arguments.length == 1 && arguments[0].equalsIgnoreCase("status")) {
+                || arguments.length == 1 && arguments[0].equalsIgnoreCase("ui")) {
+            showDialog(player, state);
+            return true;
+        }
+        if (arguments.length == 1 && arguments[0].equalsIgnoreCase("status")) {
             showStatus(player, state);
             return true;
         }
@@ -66,9 +93,13 @@ final class BaseSettingsCommand implements CommandExecutor, TabCompleter {
                 && arguments[1].equalsIgnoreCase("upgrade")) {
             return purchasePocketUpgrade(player, state);
         }
-        if (arguments.length == 3 && arguments[0].equalsIgnoreCase("pocket")
+        if (arguments.length == 4 && arguments[0].equalsIgnoreCase("pocket")
                 && arguments[1].equalsIgnoreCase("mobs")) {
-            return updatePocketMobSpawning(player, arguments[2]);
+            return updatePocketMobSpawning(player, arguments[2], arguments[3]);
+        }
+        if (arguments.length == 4 && arguments[0].equalsIgnoreCase("pocket")
+                && arguments[1].equalsIgnoreCase("type")) {
+            return purchasePocketBiome(player, arguments[2], arguments[3]);
         }
         if (arguments.length == 2 && arguments[0].equalsIgnoreCase("visitors")) {
             return updateVisitors(player, state, arguments[1]);
@@ -180,7 +211,64 @@ final class BaseSettingsCommand implements CommandExecutor, TabCompleter {
         return true;
     }
 
-    private boolean updatePocketMobSpawning(Player player, String mode) {
+    private boolean purchasePocketBiome(
+        Player player,
+        String worldTypeName,
+        String biomeName
+    ) {
+        if (pocketBases == null) {
+            player.sendMessage(ChatColor.RED + "Pocket Bases are currently unavailable.");
+            return true;
+        }
+        PocketBaseState current = pocketBases.state(player.getUniqueId());
+        if (current.level() < 1) {
+            player.sendMessage(ChatColor.RED + "Pocket Base I is still locked.");
+            return true;
+        }
+        PocketBaseBiome biome = PocketBaseWorldType.fromCommand(worldTypeName)
+            .flatMap(worldType -> PocketBaseBiome.fromCommand(worldType, biomeName))
+            .orElse(null);
+        if (biome == null) {
+            player.sendMessage(ChatColor.RED + "That Pocket Base type and subtype are invalid.");
+            return true;
+        }
+        if (biome == current.biome()) {
+            player.sendMessage(ChatColor.RED + "Your Pocket Base already uses "
+                + biome.commandName() + ".");
+            return true;
+        }
+        int price = settings.current().pocketBaseBiomeChangeCost();
+        Material currency = Material.valueOf(
+            settings.current().pocketBaseBiomeCurrencyMaterial()
+        );
+        PlayerInventory inventory = player.getInventory();
+        if (countCurrency(inventory, currency) < price) {
+            player.sendMessage(ChatColor.RED + "Changing Pocket Base biome costs "
+                + price + " " + currency.name().toLowerCase(Locale.ROOT) + ".");
+            return true;
+        }
+        ItemStack[] snapshot = cloneContents(inventory.getStorageContents());
+        removeCurrency(inventory, currency, price);
+        final PocketBaseState updated;
+        try {
+            updated = pocketBases.setBiome(player.getUniqueId(), biome);
+        } catch (IOException | RuntimeException exception) {
+            inventory.setStorageContents(snapshot);
+            player.sendMessage(ChatColor.RED
+                + "The Pocket Base biome change failed; your payment was restored.");
+            return true;
+        }
+        player.sendMessage(ChatColor.GREEN + "Pocket Base biome changed to "
+            + updated.biome().commandName() + " for " + price + " "
+            + currency.name().toLowerCase(Locale.ROOT) + ".");
+        return true;
+    }
+
+    private boolean updatePocketMobSpawning(
+        Player player,
+        String category,
+        String mode
+    ) {
         if (pocketBases == null) {
             player.sendMessage(ChatColor.RED + "Pocket Bases are currently unavailable.");
             return true;
@@ -196,17 +284,30 @@ final class BaseSettingsCommand implements CommandExecutor, TabCompleter {
             return true;
         }
         final PocketBaseState updated;
+        final boolean settingEnabled;
         try {
-            updated = pocketBases.setMobSpawning(player.getUniqueId(), enabled);
+            if (category.equalsIgnoreCase("hostile")) {
+                updated = pocketBases.setHostileMobSpawning(
+                    player.getUniqueId(), enabled
+                );
+                settingEnabled = updated.hostileMobSpawningEnabled();
+            } else if (category.equalsIgnoreCase("passive")) {
+                updated = pocketBases.setPassiveMobSpawning(
+                    player.getUniqueId(), enabled
+                );
+                settingEnabled = updated.passiveMobSpawningEnabled();
+            } else {
+                sendUsage(player);
+                return true;
+            }
         } catch (IOException | RuntimeException exception) {
             player.sendMessage(ChatColor.RED
                 + "The Pocket Base mob-spawning setting could not be changed.");
             return true;
         }
-        player.sendMessage(ChatColor.YELLOW + "Pocket Base mob spawning is now "
-            + (updated.mobSpawningEnabled()
-                ? ChatColor.GREEN + "enabled"
-                : ChatColor.RED + "disabled")
+        player.sendMessage(ChatColor.YELLOW + "Pocket Base "
+            + category.toLowerCase(Locale.ROOT) + " mob spawning is now "
+            + (settingEnabled ? ChatColor.GREEN + "enabled" : ChatColor.RED + "disabled")
             + ChatColor.YELLOW + ".");
         return true;
     }
@@ -364,6 +465,13 @@ final class BaseSettingsCommand implements CommandExecutor, TabCompleter {
         return true;
     }
 
+    private void showDialog(Player player, PlayerState state) {
+        PocketBaseState pocket = pocketBases == null
+            ? PocketBaseState.locked(state.playerId())
+            : pocketBases.state(state.playerId());
+        player.showDialog(dialogProvider.create(state, pocket));
+    }
+
     private void showStatus(Player player, PlayerState state) {
         player.sendMessage(ChatColor.GOLD + "=== Base Progress ===");
         showBasePath(player, state);
@@ -452,8 +560,12 @@ final class BaseSettingsCommand implements CommandExecutor, TabCompleter {
         player.sendMessage(colorForPrerequisite(owner.baseLevel() >= 4 && owner.base().isPresent())
             + "Pocket Base " + pocket.level() + ": " + ChatColor.GRAY + price + " "
             + settings.current().pocketBaseCurrencyMaterial().toLowerCase(Locale.ROOT)
-            + " → /basesettings pocket upgrade; mob spawning="
-            + (pocket.mobSpawningEnabled() ? "enabled" : "disabled"));
+            + " → /basesettings pocket upgrade; type="
+            + pocket.biome().worldType().commandName() + "/" + pocket.biome().commandName()
+            + "; hostile spawning="
+            + (pocket.hostileMobSpawningEnabled() ? "enabled" : "disabled")
+            + "; passive spawning="
+            + (pocket.passiveMobSpawningEnabled() ? "enabled" : "disabled"));
     }
 
     private void showCooldownPath(Player player, PlayerState state) {
@@ -485,17 +597,43 @@ final class BaseSettingsCommand implements CommandExecutor, TabCompleter {
             List<String> modes = arguments[0].equalsIgnoreCase("visitors")
                 ? VISITOR_MODES
                 : switch (arguments[0].toLowerCase(Locale.ROOT)) {
-                    case "pocket" -> List.of("upgrade", "mobs");
+                    case "pocket" -> List.of("upgrade", "mobs", "type");
                     case "navigation", "flight", "border", "spawnable", "bossbar" -> ENABLE_MODES;
                     default -> List.of();
                 };
             String prefix = arguments[1].toLowerCase(Locale.ROOT);
             return modes.stream().filter(mode -> mode.startsWith(prefix)).toList();
         }
-        if (arguments.length == 3 && arguments[0].equalsIgnoreCase("pocket")
-                && arguments[1].equalsIgnoreCase("mobs")) {
+        if (arguments.length == 3 && arguments[0].equalsIgnoreCase("pocket")) {
             String prefix = arguments[2].toLowerCase(Locale.ROOT);
-            return ENABLE_MODES.stream().filter(mode -> mode.startsWith(prefix)).toList();
+            if (arguments[1].equalsIgnoreCase("mobs")) {
+                return List.of("hostile", "passive").stream()
+                    .filter(category -> category.startsWith(prefix))
+                    .toList();
+            }
+            if (arguments[1].equalsIgnoreCase("type")) {
+                return POCKET_WORLD_TYPES.stream()
+                    .filter(type -> type.startsWith(prefix))
+                    .toList();
+            }
+        }
+        if (arguments.length == 4 && arguments[0].equalsIgnoreCase("pocket")) {
+            String prefix = arguments[3].toLowerCase(Locale.ROOT);
+            if (arguments[1].equalsIgnoreCase("mobs")
+                    && (arguments[2].equalsIgnoreCase("hostile")
+                        || arguments[2].equalsIgnoreCase("passive"))) {
+                return ENABLE_MODES.stream()
+                    .filter(mode -> mode.startsWith(prefix))
+                    .toList();
+            }
+            if (arguments[1].equalsIgnoreCase("type")) {
+                return PocketBaseWorldType.fromCommand(arguments[2])
+                    .map(PocketBaseBiome::commandNames)
+                    .orElse(List.of())
+                    .stream()
+                    .filter(biome -> biome.startsWith(prefix))
+                    .toList();
+            }
         }
         return List.of();
     }
@@ -554,9 +692,16 @@ final class BaseSettingsCommand implements CommandExecutor, TabCompleter {
         return met ? ChatColor.YELLOW : ChatColor.RED;
     }
 
+    @FunctionalInterface
+    interface DialogProvider {
+        Dialog create(PlayerState owner, PocketBaseState pocket);
+    }
+
     private static void sendUsage(Player player) {
         player.sendMessage(ChatColor.RED + "Usage: /basesettings "
-            + "[status|upgrade|pocket upgrade|pocket mobs <enable|disable>"
+            + "[ui|status|upgrade|pocket upgrade|pocket mobs "
+            + "<hostile|passive> <enable|disable>"
+            + "|pocket type <void|nether|overworld> <subtype>"
             + "|visitors <allowed|blocked>|navigation <enable|disable>"
             + "|flight <enable|disable>|border <enable|disable>"
             + "|spawnable <enable|disable>|bossbar <enable|disable>]");

src/main/java/games/dmg/spigotbase/BaseSettingsDialogFactory.java

@@ -0,0 +1,437 @@
+package games.dmg.spigotbase;
+
+import io.papermc.paper.dialog.Dialog;
+import io.papermc.paper.registry.RegistryKey;
+import io.papermc.paper.registry.data.dialog.ActionButton;
+import io.papermc.paper.registry.data.dialog.DialogBase;
+import io.papermc.paper.registry.data.dialog.action.DialogAction;
+import io.papermc.paper.registry.data.dialog.body.DialogBody;
+import io.papermc.paper.registry.data.dialog.type.DialogType;
+import io.papermc.paper.registry.set.RegistrySet;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Locale;
+import net.kyori.adventure.text.Component;
+import net.kyori.adventure.text.event.ClickEvent;
+
+final class BaseSettingsDialogFactory {
+    private static final int DIALOG_WIDTH = 420;
+    private final PluginSettings settings;
+
+    BaseSettingsDialogFactory(PluginSettings settings) {
+        this.settings = settings;
+    }
+
+    Dialog create(PlayerState owner, PocketBaseState pocket) {
+        return render(specification(owner, pocket));
+    }
+
+    DialogSpec specification(PlayerState owner, PocketBaseState pocket) {
+        List<DialogSpec> dialogs = List.of(
+            generalSettings(owner),
+            progressReport(),
+            baseUpgrade(owner),
+            pocketSettings(owner, pocket)
+        );
+        return new ListSpec(
+            content(
+                "Base Settings",
+                "Base Settings",
+                "Base " + owner.baseLevel() + "/4 • Size " + owner.sizeLevel() + "/3"
+                    + " • Flight " + owner.flightLevel() + "/3\n"
+                    + "Pocket Base " + pocket.level() + " • "
+                    + humanize(pocket.biome().commandName())
+            ),
+            dialogs,
+            2,
+            190
+        );
+    }
+
+    private DialogSpec generalSettings(PlayerState owner) {
+        List<ButtonSpec> actions = List.of(
+            toggle(
+                "Visitors",
+                owner.baseLevel() >= 4,
+                owner.visitorsEnabled(),
+                "Allowed",
+                "Blocked",
+                "basesettings visitors "
+                    + (owner.visitorsEnabled() ? "blocked" : "allowed")
+            ),
+            toggle(
+                "Navigation",
+                owner.baseLevel() >= 2,
+                owner.navigationEnabled(),
+                "Enabled",
+                "Disabled",
+                "basesettings navigation " + mode(!owner.navigationEnabled())
+            ),
+            toggle(
+                "Flight",
+                owner.flightLevel() >= 1,
+                owner.flightEnabled(),
+                "Enabled",
+                "Disabled",
+                "basesettings flight " + mode(!owner.flightEnabled())
+            ),
+            toggle(
+                "Border",
+                owner.baseLevel() >= 1 && owner.base().isPresent(),
+                owner.borderEnabled(),
+                "Enabled",
+                "Disabled",
+                "basesettings border " + mode(!owner.borderEnabled())
+            ),
+            toggle(
+                "Spawnable Overlay",
+                owner.baseLevel() >= 1
+                    && owner.base().isPresent()
+                    && owner.totalBlocksPlaced()
+                        >= settings.spawnableOverlayUnlockPlacements(),
+                owner.spawnableOverlayEnabled(),
+                "Enabled",
+                "Disabled",
+                "basesettings spawnable " + mode(!owner.spawnableOverlayEnabled())
+            ),
+            toggle(
+                "Progress Boss Bar",
+                true,
+                owner.bossBarEnabled(),
+                "Enabled",
+                "Disabled",
+                "basesettings bossbar " + mode(!owner.bossBarEnabled())
+            )
+        );
+        return new MultiSpec(
+            content(
+                "Base Controls",
+                "Base Controls",
+                "Select a setting to change it. Locked controls remain visible and explain "
+                    + "their requirement in chat when selected."
+            ),
+            actions,
+            2
+        );
+    }
+
+    private DialogSpec progressReport() {
+        return new NoticeSpec(
+            content(
+                "Progress Report",
+                "Progress Report",
+                "Display the detailed progression report in chat."
+            ),
+            commandButton("Show in Chat", "basesettings status")
+        );
+    }
+
+    private DialogSpec baseUpgrade(PlayerState owner) {
+        if (owner.baseLevel() >= 4) {
+            return notice("Base IV", "Base IV and visitor access are already unlocked.");
+        }
+        if (owner.baseLevel() < 3 || owner.base().isEmpty()) {
+            return notice(
+                "Base IV — Locked",
+                "Unlock and establish Base III before purchasing Base IV visitor access."
+            );
+        }
+        return confirmation(
+            "Unlock Base IV",
+            "Purchase visitor access for " + settings.visitorUnlockDiamondCost()
+                + " diamonds?",
+            "basesettings upgrade"
+        );
+    }
+
+    private DialogSpec pocketSettings(PlayerState owner, PocketBaseState pocket) {
+        List<DialogSpec> dialogs = List.of(
+            pocketUpgrade(owner, pocket),
+            pocketMobSettings(pocket),
+            pocketBiomeSettings(pocket)
+        );
+        return new ListSpec(
+            content(
+                "Pocket Base",
+                "Pocket Base " + pocket.level(),
+                pocket.level() == 0
+                    ? "Pocket Base is locked."
+                    : "Biome: " + pocket.biome().worldType().commandName() + "/"
+                        + pocket.biome().commandName() + "\nHostile mobs: "
+                        + enabled(pocket.hostileMobSpawningEnabled()) + " • Passive mobs: "
+                        + enabled(pocket.passiveMobSpawningEnabled())
+            ),
+            dialogs,
+            1,
+            260
+        );
+    }
+
+    private DialogSpec pocketUpgrade(PlayerState owner, PocketBaseState pocket) {
+        if (owner.baseLevel() < 4 || owner.base().isEmpty()) {
+            return notice(
+                "Pocket Upgrade — Locked",
+                "Establish Base IV before purchasing a Pocket Base."
+            );
+        }
+        int price = pocket.level() == 0
+            ? settings.pocketBaseUnlockCost()
+            : settings.pocketBaseUpgradeCost();
+        String currency = humanize(settings.pocketBaseCurrencyMaterial());
+        String title = pocket.level() == 0
+            ? "Unlock Pocket Base I"
+            : "Upgrade to Pocket Base " + (pocket.level() + 1);
+        return confirmation(
+            title,
+            "Purchase this upgrade for " + price + " " + currency + "?",
+            "basesettings pocket upgrade"
+        );
+    }
+
+    private DialogSpec pocketMobSettings(PocketBaseState pocket) {
+        if (pocket.level() < 1) {
+            return notice(
+                "Mob Spawning — Locked",
+                "Unlock Pocket Base I to control natural mob spawning."
+            );
+        }
+        List<ButtonSpec> actions = List.of(
+            toggle(
+                "Hostile Mobs",
+                true,
+                pocket.hostileMobSpawningEnabled(),
+                "Enabled",
+                "Disabled",
+                "basesettings pocket mobs hostile "
+                    + mode(!pocket.hostileMobSpawningEnabled())
+            ),
+            toggle(
+                "Passive Mobs",
+                true,
+                pocket.passiveMobSpawningEnabled(),
+                "Enabled",
+                "Disabled",
+                "basesettings pocket mobs passive "
+                    + mode(!pocket.passiveMobSpawningEnabled())
+            )
+        );
+        return new MultiSpec(
+            content(
+                "Mob Spawning",
+                "Mob Spawning",
+                "Control natural spawning independently for each mob category."
+            ),
+            actions,
+            1
+        );
+    }
+
+    private DialogSpec pocketBiomeSettings(PocketBaseState pocket) {
+        if (pocket.level() < 1) {
+            return notice(
+                "Change Biome — Locked",
+                "Unlock Pocket Base I to purchase biome changes."
+            );
+        }
+        List<DialogSpec> worldTypes = Arrays.stream(PocketBaseWorldType.values())
+            .map(type -> pocketBiomeType(pocket, type))
+            .toList();
+        return new ListSpec(
+            content(
+                "Change Biome",
+                "Change Biome",
+                "Current biome: " + pocket.biome().worldType().commandName() + "/"
+                    + pocket.biome().commandName() + "\nEach change costs "
+                    + settings.pocketBaseBiomeChangeCost() + " "
+                    + humanize(settings.pocketBaseBiomeCurrencyMaterial()) + "."
+            ),
+            worldTypes,
+            1,
+            220
+        );
+    }
+
+    private DialogSpec pocketBiomeType(
+        PocketBaseState pocket,
+        PocketBaseWorldType worldType
+    ) {
+        List<DialogSpec> biomes = Arrays.stream(PocketBaseBiome.values())
+            .filter(biome -> biome.worldType() == worldType)
+            .map(biome -> biomeConfirmation(pocket, biome))
+            .toList();
+        return new ListSpec(
+            content(
+                humanize(worldType.commandName()),
+                humanize(worldType.commandName()) + " Biomes",
+                "Choose a biome subtype. The active biome is marked as selected."
+            ),
+            biomes,
+            2,
+            190
+        );
+    }
+
+    private DialogSpec biomeConfirmation(PocketBaseState pocket, PocketBaseBiome biome) {
+        String title = humanize(biome.commandName())
+            + (pocket.biome() == biome ? " — Selected" : "");
+        if (pocket.biome() == biome) {
+            return notice(title, "This is your Pocket Base's current biome.");
+        }
+        return confirmation(
+            title,
+            "Change the Pocket Base biome for " + settings.pocketBaseBiomeChangeCost()
+                + " " + humanize(settings.pocketBaseBiomeCurrencyMaterial()) + "?",
+            "basesettings pocket type " + biome.worldType().commandName() + " "
+                + biome.commandName()
+        );
+    }
+
+    private static DialogSpec confirmation(String title, String message, String command) {
+        return new ConfirmationSpec(
+            content(title, title, message),
+            commandButton("Confirm", command)
+        );
+    }
+
+    private static DialogSpec notice(String title, String message) {
+        return new NoticeSpec(content(title, title, message), null);
+    }
+
+    private static ButtonSpec toggle(
+        String name,
+        boolean unlocked,
+        boolean active,
+        String activeLabel,
+        String inactiveLabel,
+        String command
+    ) {
+        String state = unlocked ? (active ? activeLabel : inactiveLabel) : "Locked";
+        String tooltip = unlocked
+            ? "Click to change this setting."
+            : "This setting has not been unlocked yet.";
+        return new ButtonSpec(name + ": " + state, tooltip, 190, "/" + command);
+    }
+
+    private static ButtonSpec commandButton(String label, String command) {
+        return new ButtonSpec(label, "", 150, "/" + command);
+    }
+
+    private static DialogContent content(
+        String title,
+        String externalTitle,
+        String message
+    ) {
+        return new DialogContent(title, externalTitle, message);
+    }
+
+    private static Dialog render(DialogSpec specification) {
+        DialogType type;
+        if (specification instanceof ListSpec list) {
+            List<Dialog> dialogs = list.dialogs().stream()
+                .map(BaseSettingsDialogFactory::render)
+                .toList();
+            type = DialogType.dialogList(
+                RegistrySet.valueSet(RegistryKey.DIALOG, dialogs),
+                null,
+                list.columns(),
+                list.buttonWidth()
+            );
+        } else if (specification instanceof MultiSpec multi) {
+            List<ActionButton> actions = multi.actions().stream()
+                .map(BaseSettingsDialogFactory::render)
+                .toList();
+            type = DialogType.multiAction(actions, null, multi.columns());
+        } else if (specification instanceof ConfirmationSpec confirmation) {
+            ActionButton cancel = ActionButton.builder(Component.text("Cancel")).build();
+            type = DialogType.confirmation(render(confirmation.confirm()), cancel);
+        } else if (specification instanceof NoticeSpec notice) {
+            type = notice.action() == null
+                ? DialogType.notice()
+                : DialogType.notice(render(notice.action()));
+        } else {
+            throw new IllegalArgumentException("Unsupported dialog specification");
+        }
+        DialogContent content = specification.content();
+        DialogBase base = DialogBase.builder(Component.text(content.title()))
+            .externalTitle(Component.text(content.externalTitle()))
+            .body(List.of(DialogBody.plainMessage(
+                Component.text(content.message()), DIALOG_WIDTH
+            )))
+            .canCloseWithEscape(true)
+            .pause(false)
+            .afterAction(DialogBase.DialogAfterAction.CLOSE)
+            .build();
+        return Dialog.create(factory -> factory.empty().base(base).type(type));
+    }
+
+    private static ActionButton render(ButtonSpec button) {
+        ActionButton.Builder builder = ActionButton.builder(Component.text(button.label()))
+            .width(button.width())
+            .action(DialogAction.staticAction(commandClick(button.command())));
+        if (!button.tooltip().isEmpty()) {
+            builder.tooltip(Component.text(button.tooltip()));
+        }
+        return builder.build();
+    }
+
+    static ClickEvent<ClickEvent.Payload.Text> commandClick(String command) {
+        return ClickEvent.runCommand(command);
+    }
+
+    sealed interface DialogSpec permits ListSpec, MultiSpec, ConfirmationSpec, NoticeSpec {
+        DialogContent content();
+    }
+
+    record DialogContent(String title, String externalTitle, String message) {
+    }
+
+    record ListSpec(
+        DialogContent content,
+        List<DialogSpec> dialogs,
+        int columns,
+        int buttonWidth
+    ) implements DialogSpec {
+    }
+
+    record MultiSpec(
+        DialogContent content,
+        List<ButtonSpec> actions,
+        int columns
+    ) implements DialogSpec {
+    }
+
+    record ConfirmationSpec(
+        DialogContent content,
+        ButtonSpec confirm
+    ) implements DialogSpec {
+    }
+
+    record NoticeSpec(
+        DialogContent content,
+        ButtonSpec action
+    ) implements DialogSpec {
+    }
+
+    record ButtonSpec(String label, String tooltip, int width, String command) {
+    }
+
+    private static String mode(boolean active) {
+        return active ? "enable" : "disable";
+    }
+
+    private static String enabled(boolean active) {
+        return active ? "enabled" : "disabled";
+    }
+
+    private static String humanize(String value) {
+        String normalized = value.toLowerCase(Locale.ROOT).replace('_', ' ');
+        StringBuilder result = new StringBuilder(normalized.length());
+        boolean capitalize = true;
+        for (int index = 0; index < normalized.length(); index++) {
+            char character = normalized.charAt(index);
+            result.append(capitalize ? Character.toUpperCase(character) : character);
+            capitalize = character == ' ';
+        }
+        return result.toString();
+    }
+}

src/main/java/games/dmg/spigotbase/PluginSettings.java

@@ -39,12 +39,14 @@ public record PluginSettings(
     int visitorUnlockDiamondCost,
     int pocketBaseUnlockCost,
     int pocketBaseUpgradeCost,
+    int pocketBaseBiomeChangeCost,
     Set<String> baseUnlockMaterials,
     String stoneExpansionMaterial,
     String deepslateExpansionMaterial,
     String obsidianExpansionMaterial,
     String visitorCurrencyMaterial,
     String pocketBaseCurrencyMaterial,
+    String pocketBaseBiomeCurrencyMaterial,
     String pocketBasePortalFrameMaterial,
     Set<String> cooldownExcludedMaterials,
     int bossBarDurationTicks,
@@ -85,6 +87,7 @@ public record PluginSettings(
     private static final int DEFAULT_VISITOR_UNLOCK_DIAMOND_COST = 128;
     private static final int DEFAULT_POCKET_BASE_UNLOCK_COST = 64;
     private static final int DEFAULT_POCKET_BASE_UPGRADE_COST = 16;
+    private static final int DEFAULT_POCKET_BASE_BIOME_CHANGE_COST = 16;
     private static final int DEFAULT_BOSS_BAR_DURATION_TICKS = 60;
     private static final int DEFAULT_NAVIGATION_PARTICLE_COUNT = 5;
     private static final int DEFAULT_TITLE_FADE_IN_TICKS = 10;
@@ -148,6 +151,7 @@ public record PluginSettings(
         requirePositive(visitorUnlockDiamondCost, "visitor-unlock-diamond-cost");
         requirePositive(pocketBaseUnlockCost, "pocket-base-unlock-cost");
         requirePositive(pocketBaseUpgradeCost, "pocket-base-upgrade-cost");
+        requirePositive(pocketBaseBiomeChangeCost, "pocket-base-biome-change-cost");
         baseUnlockMaterials = normalizedSet(baseUnlockMaterials, "base-unlock-materials", false);
         stoneExpansionMaterial = normalizedName(stoneExpansionMaterial, "stone-expansion-material");
         deepslateExpansionMaterial = normalizedName(
@@ -162,6 +166,9 @@ public record PluginSettings(
         pocketBaseCurrencyMaterial = normalizedName(
             pocketBaseCurrencyMaterial, "pocket-base-currency-material"
         );
+        pocketBaseBiomeCurrencyMaterial = normalizedName(
+            pocketBaseBiomeCurrencyMaterial, "pocket-base-biome-currency-material"
+        );
         pocketBasePortalFrameMaterial = normalizedName(
             pocketBasePortalFrameMaterial, "pocket-base-portal-frame-material"
         );
@@ -230,12 +237,18 @@ public record PluginSettings(
             integer(values, "visitor-unlock-diamond-cost", DEFAULT_VISITOR_UNLOCK_DIAMOND_COST),
             integer(values, "pocket-base-unlock-cost", DEFAULT_POCKET_BASE_UNLOCK_COST),
             integer(values, "pocket-base-upgrade-cost", DEFAULT_POCKET_BASE_UPGRADE_COST),
+            integer(
+                values,
+                "pocket-base-biome-change-cost",
+                DEFAULT_POCKET_BASE_BIOME_CHANGE_COST
+            ),
             stringSet(values, "base-unlock-materials", Set.of("GRASS_BLOCK", "DIRT")),
             string(values, "stone-expansion-material", "STONE"),
             string(values, "deepslate-expansion-material", "DEEPSLATE"),
             string(values, "obsidian-expansion-material", "OBSIDIAN"),
             string(values, "visitor-currency-material", "DIAMOND"),
             string(values, "pocket-base-currency-material", "DIAMOND_BLOCK"),
+            string(values, "pocket-base-biome-currency-material", "NETHERITE_BLOCK"),
             string(values, "pocket-base-portal-frame-material", "DIAMOND_BLOCK"),
             stringSet(values, "cooldown-excluded-materials", Set.of()),
             integer(values, "boss-bar-duration-ticks", DEFAULT_BOSS_BAR_DURATION_TICKS),

src/main/java/games/dmg/spigotbase/PluginSettingsValidator.java

@@ -29,6 +29,10 @@ final class PluginSettingsValidator {
         }
         validateCurrency(settings.visitorCurrencyMaterial(), "visitor-currency-material");
         validateCurrency(settings.pocketBaseCurrencyMaterial(), "pocket-base-currency-material");
+        validateCurrency(
+            settings.pocketBaseBiomeCurrencyMaterial(),
+            "pocket-base-biome-currency-material"
+        );
         return settings;
     }
 

src/main/java/games/dmg/spigotbase/PocketBaseBiome.java

@@ -0,0 +1,105 @@
+package games.dmg.spigotbase;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Locale;
+import java.util.Optional;
+
+public enum PocketBaseBiome {
+    THE_VOID(PocketBaseWorldType.VOID),
+
+    NETHER_WASTES(PocketBaseWorldType.NETHER),
+    SOUL_SAND_VALLEY(PocketBaseWorldType.NETHER),
+    CRIMSON_FOREST(PocketBaseWorldType.NETHER),
+    WARPED_FOREST(PocketBaseWorldType.NETHER),
+    BASALT_DELTAS(PocketBaseWorldType.NETHER),
+
+    OCEAN(PocketBaseWorldType.OVERWORLD),
+    PLAINS(PocketBaseWorldType.OVERWORLD),
+    DESERT(PocketBaseWorldType.OVERWORLD),
+    WINDSWEPT_HILLS(PocketBaseWorldType.OVERWORLD),
+    FOREST(PocketBaseWorldType.OVERWORLD),
+    TAIGA(PocketBaseWorldType.OVERWORLD),
+    SWAMP(PocketBaseWorldType.OVERWORLD),
+    MANGROVE_SWAMP(PocketBaseWorldType.OVERWORLD),
+    RIVER(PocketBaseWorldType.OVERWORLD),
+    FROZEN_OCEAN(PocketBaseWorldType.OVERWORLD),
+    FROZEN_RIVER(PocketBaseWorldType.OVERWORLD),
+    SNOWY_PLAINS(PocketBaseWorldType.OVERWORLD),
+    MUSHROOM_FIELDS(PocketBaseWorldType.OVERWORLD),
+    BEACH(PocketBaseWorldType.OVERWORLD),
+    JUNGLE(PocketBaseWorldType.OVERWORLD),
+    SPARSE_JUNGLE(PocketBaseWorldType.OVERWORLD),
+    DEEP_OCEAN(PocketBaseWorldType.OVERWORLD),
+    STONY_SHORE(PocketBaseWorldType.OVERWORLD),
+    SNOWY_BEACH(PocketBaseWorldType.OVERWORLD),
+    BIRCH_FOREST(PocketBaseWorldType.OVERWORLD),
+    DARK_FOREST(PocketBaseWorldType.OVERWORLD),
+    PALE_GARDEN(PocketBaseWorldType.OVERWORLD),
+    SNOWY_TAIGA(PocketBaseWorldType.OVERWORLD),
+    OLD_GROWTH_PINE_TAIGA(PocketBaseWorldType.OVERWORLD),
+    WINDSWEPT_FOREST(PocketBaseWorldType.OVERWORLD),
+    SAVANNA(PocketBaseWorldType.OVERWORLD),
+    SAVANNA_PLATEAU(PocketBaseWorldType.OVERWORLD),
+    BADLANDS(PocketBaseWorldType.OVERWORLD),
+    WOODED_BADLANDS(PocketBaseWorldType.OVERWORLD),
+    WARM_OCEAN(PocketBaseWorldType.OVERWORLD),
+    LUKEWARM_OCEAN(PocketBaseWorldType.OVERWORLD),
+    COLD_OCEAN(PocketBaseWorldType.OVERWORLD),
+    DEEP_LUKEWARM_OCEAN(PocketBaseWorldType.OVERWORLD),
+    DEEP_COLD_OCEAN(PocketBaseWorldType.OVERWORLD),
+    DEEP_FROZEN_OCEAN(PocketBaseWorldType.OVERWORLD),
+    SUNFLOWER_PLAINS(PocketBaseWorldType.OVERWORLD),
+    WINDSWEPT_GRAVELLY_HILLS(PocketBaseWorldType.OVERWORLD),
+    FLOWER_FOREST(PocketBaseWorldType.OVERWORLD),
+    ICE_SPIKES(PocketBaseWorldType.OVERWORLD),
+    OLD_GROWTH_BIRCH_FOREST(PocketBaseWorldType.OVERWORLD),
+    OLD_GROWTH_SPRUCE_TAIGA(PocketBaseWorldType.OVERWORLD),
+    WINDSWEPT_SAVANNA(PocketBaseWorldType.OVERWORLD),
+    ERODED_BADLANDS(PocketBaseWorldType.OVERWORLD),
+    BAMBOO_JUNGLE(PocketBaseWorldType.OVERWORLD),
+    DRIPSTONE_CAVES(PocketBaseWorldType.OVERWORLD),
+    LUSH_CAVES(PocketBaseWorldType.OVERWORLD),
+    DEEP_DARK(PocketBaseWorldType.OVERWORLD),
+    SULFUR_CAVES(PocketBaseWorldType.OVERWORLD),
+    MEADOW(PocketBaseWorldType.OVERWORLD),
+    GROVE(PocketBaseWorldType.OVERWORLD),
+    SNOWY_SLOPES(PocketBaseWorldType.OVERWORLD),
+    FROZEN_PEAKS(PocketBaseWorldType.OVERWORLD),
+    JAGGED_PEAKS(PocketBaseWorldType.OVERWORLD),
+    STONY_PEAKS(PocketBaseWorldType.OVERWORLD),
+    CHERRY_GROVE(PocketBaseWorldType.OVERWORLD);
+
+    private final PocketBaseWorldType worldType;
+
+    PocketBaseBiome(PocketBaseWorldType worldType) {
+        this.worldType = worldType;
+    }
+
+    public PocketBaseWorldType worldType() {
+        return worldType;
+    }
+
+    public String commandName() {
+        return name().toLowerCase(Locale.ROOT);
+    }
+
+    static Optional<PocketBaseBiome> fromCommand(
+        PocketBaseWorldType worldType,
+        String value
+    ) {
+        try {
+            PocketBaseBiome biome = valueOf(value.toUpperCase(Locale.ROOT));
+            return biome.worldType == worldType ? Optional.of(biome) : Optional.empty();
+        } catch (IllegalArgumentException exception) {
+            return Optional.empty();
+        }
+    }
+
+    static List<String> commandNames(PocketBaseWorldType worldType) {
+        return Arrays.stream(values())
+            .filter(biome -> biome.worldType == worldType)
+            .map(PocketBaseBiome::commandName)
+            .toList();
+    }
+}

src/main/java/games/dmg/spigotbase/PocketBaseController.java

@@ -5,6 +5,7 @@ import java.util.HashMap;
 import java.util.Map;
 import java.util.Optional;
 import java.util.UUID;
+import java.util.function.Consumer;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import org.bukkit.ChatColor;
@@ -15,6 +16,7 @@ import org.bukkit.Server;
 import org.bukkit.World;
 import org.bukkit.block.Block;
 import org.bukkit.entity.Entity;
+import org.bukkit.entity.Mob;
 import org.bukkit.entity.Player;
 import org.bukkit.event.EventHandler;
 import org.bukkit.event.EventPriority;
@@ -26,6 +28,7 @@ import org.bukkit.event.entity.EntityDamageEvent;
 import org.bukkit.event.player.PlayerInteractEvent;
 import org.bukkit.event.player.PlayerMoveEvent;
 import org.bukkit.event.player.PlayerTeleportEvent;
+import org.bukkit.util.BoundingBox;
 
 final class PocketBaseController implements Listener, Runnable {
     private static final int VOID_RETURN_Y = -64;
@@ -63,6 +66,7 @@ final class PocketBaseController implements Listener, Runnable {
                 showPortal(pocketBases.returnPortal(state.ownerId()));
             }
         }
+        scanMobPortals();
         long now = System.nanoTime();
         cooldownUntil.entrySet().removeIf(entry -> entry.getValue() <= now);
     }
@@ -235,23 +239,62 @@ final class PocketBaseController implements Listener, Runnable {
         deactivate(ownerId);
     }
 
-    private void leavePocket(Player player, UUID ownerId) {
+    void scanMobPortals() {
+        for (PocketBaseState state : pocketBases.knownStates().values()) {
+            if (state.entrance().isPresent()) {
+                PocketPortalLocation entrance = state.entrance().orElseThrow();
+                if (isIntact(entrance)) {
+                    transportMobs(
+                        entrance,
+                        mob -> teleport(mob, pocketBases.pocketArrival(state.ownerId()))
+                    );
+                }
+            }
+            if (state.level() > 0 && pocketBases.returnPortalIsIntact(state.ownerId())) {
+                transportMobs(
+                    pocketBases.returnPortal(state.ownerId()),
+                    mob -> leavePocket(mob, state.ownerId())
+                );
+            }
+        }
+    }
+
+    private void transportMobs(
+        PocketPortalLocation portal,
+        Consumer<Mob> transport
+    ) {
+        World world = server.getWorld(portal.worldId());
+        if (world == null) {
+            return;
+        }
+        for (Entity entity : world.getNearbyEntities(
+            portalBounds(portal),
+            candidate -> candidate instanceof Mob
+        )) {
+            if (entity instanceof Mob mob && !onCooldown(mob)) {
+                transport.accept(mob);
+            }
+        }
+    }
+
+    private void leavePocket(Entity entity, UUID ownerId) {
         PocketBaseState state = pocketBases.state(ownerId);
         if (state.entrance().isPresent() && isIntact(state.entrance().orElseThrow())) {
-            teleport(player, outsidePortal(state.entrance().orElseThrow()));
+            teleport(entity, outsidePortal(state.entrance().orElseThrow()));
             return;
         }
         World fallbackWorld = server.getWorlds().get(0);
-        teleport(player, fallbackWorld.getSpawnLocation());
+        teleport(entity, fallbackWorld.getSpawnLocation());
     }
 
-    private void teleport(Player player, Location destination) {
-        cooldownUntil.put(player.getUniqueId(), System.nanoTime() + PORTAL_COOLDOWN_NANOS);
-        player.teleport(destination, PlayerTeleportEvent.TeleportCause.PLUGIN);
+    private void teleport(Entity entity, Location destination) {
+        cooldownUntil.put(entity.getUniqueId(), System.nanoTime() + PORTAL_COOLDOWN_NANOS);
+        entity.setFallDistance(0.0F);
+        entity.teleport(destination, PlayerTeleportEvent.TeleportCause.PLUGIN);
     }
 
-    private boolean onCooldown(Player player) {
-        return cooldownUntil.getOrDefault(player.getUniqueId(), 0L) > System.nanoTime();
+    private boolean onCooldown(Entity entity) {
+        return cooldownUntil.getOrDefault(entity.getUniqueId(), 0L) > System.nanoTime();
     }
 
     private void validateEntrances() {
@@ -320,6 +363,26 @@ final class PocketBaseController implements Listener, Runnable {
             : new Location(world, portal.x() + 1.5, portal.y() + 1.0, portal.z() + 2.0);
     }
 
+    private static BoundingBox portalBounds(PocketPortalLocation portal) {
+        return portal.axis() == PocketPortalAxis.X
+            ? new BoundingBox(
+                portal.x() + 1.0,
+                portal.y() + 1.0,
+                portal.z(),
+                portal.x() + 3.0,
+                portal.y() + 4.0,
+                portal.z() + 1.0
+            )
+            : new BoundingBox(
+                portal.x(),
+                portal.y() + 1.0,
+                portal.z() + 1.0,
+                portal.x() + 1.0,
+                portal.y() + 4.0,
+                portal.z() + 3.0
+            );
+    }
+
     private static boolean isAir(Material material) {
         return material == Material.AIR || material == Material.CAVE_AIR
             || material == Material.VOID_AIR;

src/main/java/games/dmg/spigotbase/PocketBaseManager.java

@@ -38,7 +38,7 @@ final class PocketBaseManager {
         PocketBaseState current = states.state(ownerId);
         int nextLevel = Math.addExact(current.level(), 1);
         policy.size(nextLevel);
-        worlds.expand(ownerId, current.level(), nextLevel);
+        worlds.expand(ownerId, current.level(), nextLevel, current.biome());
         return states.updateAndSave(ownerId, state -> state.withLevel(nextLevel));
     }
 
@@ -71,20 +71,69 @@ final class PocketBaseManager {
         return states.updateAndSave(ownerId, state -> state.withReturnPortal(portal));
     }
 
-    PocketBaseState setMobSpawning(UUID ownerId, boolean enabled) throws IOException {
+    PocketBaseState setBiome(UUID ownerId, PocketBaseBiome biome) throws IOException {
         PocketBaseState current = states.state(ownerId);
         if (current.level() < 1) {
             throw new IllegalStateException("Pocket Base I is still locked");
         }
-        worlds.setMobSpawning(ownerId, enabled);
+        if (current.biome() == biome) {
+            throw new IllegalArgumentException("Pocket Base already uses that biome");
+        }
         try {
-            return states.updateAndSave(
-                ownerId,
-                state -> state.withMobSpawningEnabled(enabled)
-            );
+            worlds.setBiome(ownerId, current.level(), biome);
+            return states.updateAndSave(ownerId, state -> state.withBiome(biome));
         } catch (IOException | RuntimeException exception) {
             try {
-                worlds.setMobSpawning(ownerId, current.mobSpawningEnabled());
+                worlds.setBiome(ownerId, current.level(), current.biome());
+            } catch (RuntimeException rollbackFailure) {
+                exception.addSuppressed(rollbackFailure);
+            }
+            throw exception;
+        }
+    }
+
+    PocketBaseState setHostileMobSpawning(UUID ownerId, boolean enabled)
+            throws IOException {
+        PocketBaseState current = states.state(ownerId);
+        return setMobSpawning(
+            current,
+            enabled,
+            current.passiveMobSpawningEnabled(),
+            state -> state.withHostileMobSpawningEnabled(enabled)
+        );
+    }
+
+    PocketBaseState setPassiveMobSpawning(UUID ownerId, boolean enabled)
+            throws IOException {
+        PocketBaseState current = states.state(ownerId);
+        return setMobSpawning(
+            current,
+            current.hostileMobSpawningEnabled(),
+            enabled,
+            state -> state.withPassiveMobSpawningEnabled(enabled)
+        );
+    }
+
+    private PocketBaseState setMobSpawning(
+        PocketBaseState current,
+        boolean hostileEnabled,
+        boolean passiveEnabled,
+        java.util.function.UnaryOperator<PocketBaseState> update
+    ) throws IOException {
+        if (current.level() < 1) {
+            throw new IllegalStateException("Pocket Base I is still locked");
+        }
+        UUID ownerId = current.ownerId();
+        worlds.setMobSpawning(ownerId, hostileEnabled, passiveEnabled);
+        try {
+            return states.updateAndSave(ownerId, update);
+        } catch (IOException | RuntimeException exception) {
+            try {
+                worlds.setMobSpawning(
+                    ownerId,
+                    current.hostileMobSpawningEnabled(),
+                    current.passiveMobSpawningEnabled()
+                );
             } catch (RuntimeException rollbackFailure) {
                 exception.addSuppressed(rollbackFailure);
             }

src/main/java/games/dmg/spigotbase/PocketBaseState.java

@@ -8,7 +8,9 @@ public record PocketBaseState(
     int level,
     Optional<PocketPortalLocation> entrance,
     Optional<PocketPortalLocation> returnPortal,
-    boolean mobSpawningEnabled
+    boolean hostileMobSpawningEnabled,
+    boolean passiveMobSpawningEnabled,
+    PocketBaseBiome biome
 ) {
     public PocketBaseState {
         if (ownerId == null) {
@@ -19,6 +21,7 @@ public record PocketBaseState(
         }
         entrance = entrance == null ? Optional.empty() : entrance;
         returnPortal = returnPortal == null ? Optional.empty() : returnPortal;
+        biome = biome == null ? PocketBaseBiome.THE_VOID : biome;
         if (level == 0 && (entrance.isPresent() || returnPortal.isPresent())) {
             throw new IllegalArgumentException("a locked Pocket Base cannot have a portal");
         }
@@ -29,49 +32,65 @@ public record PocketBaseState(
         int level,
         Optional<PocketPortalLocation> entrance
     ) {
-        this(ownerId, level, entrance, Optional.empty(), false);
-    }
-
-    public PocketBaseState(
-        UUID ownerId,
-        int level,
-        Optional<PocketPortalLocation> entrance,
-        boolean mobSpawningEnabled
-    ) {
-        this(ownerId, level, entrance, Optional.empty(), mobSpawningEnabled);
+        this(
+            ownerId, level, entrance, Optional.empty(), false, false,
+            PocketBaseBiome.THE_VOID
+        );
     }
 
     public static PocketBaseState locked(UUID ownerId) {
         return new PocketBaseState(
-            ownerId, 0, Optional.empty(), Optional.empty(), false
+            ownerId, 0, Optional.empty(), Optional.empty(), false, false,
+            PocketBaseBiome.THE_VOID
         );
     }
 
     public PocketBaseState withLevel(int newLevel) {
         return new PocketBaseState(
-            ownerId, newLevel, entrance, returnPortal, mobSpawningEnabled
+            ownerId, newLevel, entrance, returnPortal, hostileMobSpawningEnabled,
+            passiveMobSpawningEnabled, biome
         );
     }
 
     public PocketBaseState withEntrance(PocketPortalLocation portal) {
         return new PocketBaseState(
-            ownerId, level, Optional.of(portal), returnPortal, mobSpawningEnabled
+            ownerId, level, Optional.of(portal), returnPortal,
+            hostileMobSpawningEnabled, passiveMobSpawningEnabled, biome
         );
     }
 
     public PocketBaseState withoutEntrance() {
         return new PocketBaseState(
-            ownerId, level, Optional.empty(), returnPortal, mobSpawningEnabled
+            ownerId, level, Optional.empty(), returnPortal, hostileMobSpawningEnabled,
+            passiveMobSpawningEnabled, biome
         );
     }
 
     public PocketBaseState withReturnPortal(PocketPortalLocation portal) {
         return new PocketBaseState(
-            ownerId, level, entrance, Optional.of(portal), mobSpawningEnabled
+            ownerId, level, entrance, Optional.of(portal), hostileMobSpawningEnabled,
+            passiveMobSpawningEnabled, biome
         );
     }
 
-    public PocketBaseState withMobSpawningEnabled(boolean enabled) {
-        return new PocketBaseState(ownerId, level, entrance, returnPortal, enabled);
+    public PocketBaseState withHostileMobSpawningEnabled(boolean enabled) {
+        return new PocketBaseState(
+            ownerId, level, entrance, returnPortal, enabled,
+            passiveMobSpawningEnabled, biome
+        );
+    }
+
+    public PocketBaseState withPassiveMobSpawningEnabled(boolean enabled) {
+        return new PocketBaseState(
+            ownerId, level, entrance, returnPortal, hostileMobSpawningEnabled,
+            enabled, biome
+        );
+    }
+
+    public PocketBaseState withBiome(PocketBaseBiome selectedBiome) {
+        return new PocketBaseState(
+            ownerId, level, entrance, returnPortal, hostileMobSpawningEnabled,
+            passiveMobSpawningEnabled, selectedBiome
+        );
     }
 }

src/main/java/games/dmg/spigotbase/PocketBaseWorldService.java

@@ -4,11 +4,15 @@ import java.util.HashMap;
 import java.util.Map;
 import java.util.Optional;
 import java.util.UUID;
+import java.util.function.Function;
 import org.bukkit.Location;
 import org.bukkit.Material;
+import org.bukkit.NamespacedKey;
+import org.bukkit.Registry;
 import org.bukkit.Server;
 import org.bukkit.World;
 import org.bukkit.WorldCreator;
+import org.bukkit.block.Biome;
 
 final class PocketBaseWorldService {
     private static final int PLATFORM_Y = 64;
@@ -16,23 +20,47 @@ final class PocketBaseWorldService {
     private final Server server;
     private final PluginSettingsProvider settings;
     private final PocketBasePolicy policy;
+    private final Function<PocketBaseBiome, Biome> biomeResolver;
     private final Map<UUID, UUID> ownersByWorld = new HashMap<>();
 
     PocketBaseWorldService(Server server, PluginSettingsProvider settings) {
+        this(server, settings, biome -> resolveBiome(server, biome));
+    }
+
+    PocketBaseWorldService(
+        Server server,
+        PluginSettingsProvider settings,
+        Function<PocketBaseBiome, Biome> biomeResolver
+    ) {
         this.server = server;
         this.settings = settings;
         this.policy = new PocketBasePolicy(settings);
+        this.biomeResolver = biomeResolver;
     }
 
     void loadExisting(Map<UUID, PocketBaseState> states) {
         for (PocketBaseState state : states.values()) {
             if (state.level() > 0) {
-                setMobSpawning(state.ownerId(), state.mobSpawningEnabled());
+                setBiome(state.ownerId(), state.level(), state.biome());
+                setMobSpawning(
+                    state.ownerId(),
+                    state.hostileMobSpawningEnabled(),
+                    state.passiveMobSpawningEnabled()
+                );
             }
         }
     }
 
     World expand(UUID ownerId, int previousLevel, int newLevel) {
+        return expand(ownerId, previousLevel, newLevel, PocketBaseBiome.THE_VOID);
+    }
+
+    World expand(
+        UUID ownerId,
+        int previousLevel,
+        int newLevel,
+        PocketBaseBiome biome
+    ) {
         World world = ensureWorld(ownerId);
         int newHalfSize = policy.size(newLevel) / 2;
         int previousHalfSize = previousLevel == 0 ? 0 : policy.size(previousLevel) / 2;
@@ -50,6 +78,7 @@ final class PocketBaseWorldService {
                 world.getBlockAt(x, PLATFORM_Y, z).setType(Material.GRASS_BLOCK, false);
             }
         }
+        applyBiome(world, previousLevel, newLevel, biome);
         if (previousLevel == 0) {
             createReturnPortal(world);
             world.setSpawnLocation(0, PLATFORM_Y + 1, 5);
@@ -66,8 +95,18 @@ final class PocketBaseWorldService {
         return ensureWorld(ownerId);
     }
 
-    void setMobSpawning(UUID ownerId, boolean enabled) {
-        ensureWorld(ownerId).setSpawnFlags(enabled, enabled);
+    void setMobSpawning(
+        UUID ownerId,
+        boolean hostileEnabled,
+        boolean passiveEnabled
+    ) {
+        ensureWorld(ownerId).setSpawnFlags(hostileEnabled, passiveEnabled);
+    }
+
+    void setBiome(UUID ownerId, int level, PocketBaseBiome biome) {
+        World world = ensureWorld(ownerId);
+        applyBiome(world, 0, level, biome);
+        world.save();
     }
 
     Location arrival(UUID ownerId) {
@@ -98,7 +137,7 @@ final class PocketBaseWorldService {
         World world = server.getWorld(name);
         boolean created = world == null;
         if (created) {
-            WorldCreator creator = new WorldCreator(name)
+            WorldCreator creator = new WorldCreator(NamespacedKey.minecraft(name))
                 .environment(World.Environment.NORMAL)
                 .generator(new VoidPocketChunkGenerator())
                 .generateStructures(false);
@@ -114,6 +153,40 @@ final class PocketBaseWorldService {
         return world;
     }
 
+    private void applyBiome(
+        World world,
+        int previousLevel,
+        int newLevel,
+        PocketBaseBiome selectedBiome
+    ) {
+        int newHalfSize = policy.size(newLevel) / 2;
+        int previousHalfSize = previousLevel == 0 ? 0 : policy.size(previousLevel) / 2;
+        Biome biome = biomeResolver.apply(selectedBiome);
+        for (int x = -newHalfSize; x < newHalfSize; x += 4) {
+            for (int z = -newHalfSize; z < newHalfSize; z += 4) {
+                boolean previouslyUnlocked = previousLevel > 0
+                    && x >= -previousHalfSize && x < previousHalfSize
+                    && z >= -previousHalfSize && z < previousHalfSize;
+                if (previouslyUnlocked) {
+                    continue;
+                }
+                for (int y = world.getMinHeight(); y < world.getMaxHeight(); y += 4) {
+                    world.setBiome(x, y, z, biome);
+                }
+            }
+        }
+    }
+
+    private static Biome resolveBiome(Server server, PocketBaseBiome selectedBiome) {
+        Registry<Biome> biomeRegistry = server.getRegistry(Biome.class);
+        if (biomeRegistry == null) {
+            throw new IllegalStateException("Biome registry is unavailable");
+        }
+        return biomeRegistry.getOrThrow(
+            NamespacedKey.minecraft(selectedBiome.commandName())
+        );
+    }
+
     private void createReturnPortal(World world) {
         PocketPortalLocation portal = new PocketPortalLocation(
             world.getUID(), world.getName(), -2, PLATFORM_Y + 1, 0, PocketPortalAxis.X

src/main/java/games/dmg/spigotbase/PocketBaseWorldType.java

@@ -0,0 +1,22 @@
+package games.dmg.spigotbase;
+
+import java.util.Locale;
+import java.util.Optional;
+
+public enum PocketBaseWorldType {
+    VOID,
+    NETHER,
+    OVERWORLD;
+
+    public String commandName() {
+        return name().toLowerCase(Locale.ROOT);
+    }
+
+    static Optional<PocketBaseWorldType> fromCommand(String value) {
+        try {
+            return Optional.of(valueOf(value.toUpperCase(Locale.ROOT)));
+        } catch (IllegalArgumentException exception) {
+            return Optional.empty();
+        }
+    }
+}

src/main/java/games/dmg/spigotbase/YamlPocketBaseRepository.java

@@ -44,7 +44,9 @@ public final class YamlPocketBaseRepository {
                     level,
                     loadPortal(yaml, path + ".entrance"),
                     loadPortal(yaml, path + ".return-portal"),
-                    yaml.getBoolean(path + ".mob-spawning-enabled", false)
+                    loadMobPreference(yaml, path, "hostile-mob-spawning-enabled"),
+                    loadMobPreference(yaml, path, "passive-mob-spawning-enabled"),
+                    loadBiome(yaml, path)
                 );
                 states.put(ownerId, state);
             } catch (IllegalArgumentException ignored) {
@@ -63,7 +65,16 @@ public final class YamlPocketBaseRepository {
         for (PocketBaseState state : states.values()) {
             String path = "owners." + state.ownerId();
             yaml.set(path + ".level", state.level());
-            yaml.set(path + ".mob-spawning-enabled", state.mobSpawningEnabled());
+            yaml.set(
+                path + ".hostile-mob-spawning-enabled",
+                state.hostileMobSpawningEnabled()
+            );
+            yaml.set(
+                path + ".passive-mob-spawning-enabled",
+                state.passiveMobSpawningEnabled()
+            );
+            yaml.set(path + ".world-type", state.biome().worldType().commandName());
+            yaml.set(path + ".biome", state.biome().commandName());
             state.entrance().ifPresent(portal -> savePortal(yaml, path + ".entrance", portal));
             state.returnPortal().ifPresent(portal ->
                 savePortal(yaml, path + ".return-portal", portal)
@@ -87,6 +98,28 @@ public final class YamlPocketBaseRepository {
         }
     }
 
+    private static boolean loadMobPreference(
+        YamlConfiguration yaml,
+        String path,
+        String categoryKey
+    ) {
+        return yaml.getBoolean(
+            path + "." + categoryKey,
+            yaml.getBoolean(path + ".mob-spawning-enabled", false)
+        );
+    }
+
+    private static PocketBaseBiome loadBiome(YamlConfiguration yaml, String path) {
+        String worldTypeName = yaml.getString(path + ".world-type");
+        String biomeName = yaml.getString(path + ".biome");
+        if (worldTypeName == null || biomeName == null) {
+            return PocketBaseBiome.THE_VOID;
+        }
+        return PocketBaseWorldType.fromCommand(worldTypeName)
+            .flatMap(worldType -> PocketBaseBiome.fromCommand(worldType, biomeName))
+            .orElse(PocketBaseBiome.THE_VOID);
+    }
+
     private static Optional<PocketPortalLocation> loadPortal(
         YamlConfiguration yaml,
         String path

src/main/resources/config.yml

@@ -50,6 +50,8 @@ visitor-currency-material: DIAMOND
 pocket-base-unlock-cost: 64
 pocket-base-upgrade-cost: 16
 pocket-base-currency-material: DIAMOND_BLOCK
+pocket-base-biome-change-cost: 16
+pocket-base-biome-currency-material: NETHERITE_BLOCK
 pocket-base-portal-frame-material: DIAMOND_BLOCK
 
 # Spawnable block overlay

src/main/resources/plugin.yml

@@ -19,7 +19,7 @@ commands:
     aliases: [visit]
   basesettings:
     description: View progression, upgrade, and manage base settings.
-    usage: /basesettings [status|upgrade|pocket|visitors|navigation|flight|border|spawnable|bossbar]
+    usage: /basesettings [ui|status|upgrade|pocket|visitors|navigation|flight|border|spawnable|bossbar]
     aliases: [homesettings]
   baseadmin:
     description: Administer Spigot Base.

src/test/java/games/dmg/spigotbase/BaseSettingsCommandTest.java

@@ -20,13 +20,29 @@ import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.UnaryOperator;
 import org.bukkit.ChatColor;
 import org.bukkit.Material;
+import org.bukkit.command.CommandSender;
 import org.bukkit.entity.Player;
 import org.bukkit.inventory.ItemStack;
 import org.bukkit.inventory.PlayerInventory;
+import net.kyori.adventure.dialog.DialogLike;
 import org.junit.jupiter.api.Test;
 import org.mockito.ArgumentCaptor;
 
 final class BaseSettingsCommandTest {
+    @Test
+    void rejectsNonPlayerExecution() {
+        CommandSender sender = mock(CommandSender.class);
+        BaseSettingsCommand command = new BaseSettingsCommand(
+            mock(BaseStateManager.class),
+            new PluginSettingsProvider(PluginSettings.from(Map.of())),
+            mock(BaseFlightController.class)
+        );
+
+        command.onCommand(sender, null, "basesettings", new String[0]);
+
+        verify(sender).sendMessage("Only players have base progression.");
+    }
+
     @Test
     void spawnableEnableIsIdempotentAfterUnlock() {
         UUID playerId = UUID.randomUUID();
@@ -100,10 +116,42 @@ final class BaseSettingsCommandTest {
             List.of("mobs"),
             command.onTabComplete(null, null, "basesettings", new String[] {"pocket", "m"})
         );
+        assertEquals(
+            List.of("type"),
+            command.onTabComplete(null, null, "basesettings", new String[] {"pocket", "t"})
+        );
+        assertEquals(
+            List.of("nether"),
+            command.onTabComplete(
+                null, null, "basesettings", new String[] {"pocket", "type", "n"}
+            )
+        );
+        assertEquals(
+            List.of("crimson_forest"),
+            command.onTabComplete(
+                null,
+                null,
+                "basesettings",
+                new String[] {"pocket", "type", "nether", "c"}
+            )
+        );
+        assertEquals(
+            List.of("hostile"),
+            command.onTabComplete(
+                null, null, "basesettings", new String[] {"pocket", "mobs", "h"}
+            )
+        );
+        assertEquals(
+            List.of("passive"),
+            command.onTabComplete(
+                null, null, "basesettings", new String[] {"pocket", "mobs", "p"}
+            )
+        );
         assertEquals(
             List.of("enable"),
             command.onTabComplete(
-                null, null, "basesettings", new String[] {"pocket", "mobs", "e"}
+                null, null, "basesettings",
+                new String[] {"pocket", "mobs", "hostile", "e"}
             )
         );
         for (String setting : List.of("navigation", "flight", "border", "spawnable", "bossbar")) {
@@ -124,8 +172,8 @@ final class BaseSettingsCommandTest {
 
         assertEquals(
             List.of(
-                "status", "upgrade", "pocket", "visitors", "navigation", "flight", "border",
-                "spawnable", "bossbar"
+                "ui", "status", "upgrade", "pocket", "visitors", "navigation", "flight",
+                "border", "spawnable", "bossbar"
             ),
             command.onTabComplete(null, null, "basesettings", new String[] {""})
         );
@@ -138,10 +186,12 @@ final class BaseSettingsCommandTest {
         when(player.getUniqueId()).thenReturn(playerId);
         when(player.getName()).thenReturn("Host");
         PlayerInventory inventory = mock(PlayerInventory.class);
+        ItemStack firstStack = item(Material.DIAMOND, 64);
+        ItemStack secondStack = item(Material.DIAMOND, 64);
         when(player.getInventory()).thenReturn(inventory);
         when(inventory.getStorageContents()).thenReturn(new ItemStack[] {
-            new ItemStack(Material.DIAMOND, 64),
-            new ItemStack(Material.DIAMOND, 64)
+            firstStack,
+            secondStack
         });
 
         PlayerState current = PlayerState.newPlayer(playerId, "Host")
@@ -179,10 +229,9 @@ final class BaseSettingsCommandTest {
         when(player.getUniqueId()).thenReturn(playerId);
         when(player.getName()).thenReturn("Builder");
         PlayerInventory inventory = mock(PlayerInventory.class);
+        ItemStack currency = item(Material.DIAMOND_BLOCK, 64);
         when(player.getInventory()).thenReturn(inventory);
-        when(inventory.getStorageContents()).thenReturn(new ItemStack[] {
-            new ItemStack(Material.DIAMOND_BLOCK, 64)
-        });
+        when(inventory.getStorageContents()).thenReturn(new ItemStack[] {currency});
         PlayerState owner = PlayerState.newPlayer(playerId, "Builder")
             .withAdministrativeLevels(4, 0, 0, 0, 0, false, false, true)
             .withBase(
@@ -210,20 +259,52 @@ final class BaseSettingsCommandTest {
     }
 
     @Test
-    void pocketOwnerCanEnableNaturalMobSpawning() throws Exception {
+    void pocketOwnerCanPurchaseBiomeChangeWithConfiguredCurrency() throws Exception {
         UUID playerId = UUID.randomUUID();
         Player player = mock(Player.class);
         when(player.getUniqueId()).thenReturn(playerId);
         when(player.getName()).thenReturn("Builder");
+        PlayerInventory inventory = mock(PlayerInventory.class);
+        ItemStack currency = item(Material.NETHERITE_BLOCK, 16);
+        when(player.getInventory()).thenReturn(inventory);
+        when(inventory.getStorageContents()).thenReturn(new ItemStack[] {currency});
+        BaseStateManager stateManager = mock(BaseStateManager.class);
+        when(stateManager.player(playerId, "Builder"))
+            .thenReturn(PlayerState.newPlayer(playerId, "Builder"));
+        PocketBaseManager pocketBases = mock(PocketBaseManager.class);
+        PocketBaseState current = new PocketBaseState(playerId, 1, java.util.Optional.empty());
+        when(pocketBases.state(playerId)).thenReturn(current);
+        when(pocketBases.setBiome(playerId, PocketBaseBiome.CRIMSON_FOREST))
+            .thenReturn(current.withBiome(PocketBaseBiome.CRIMSON_FOREST));
+        BaseSettingsCommand command = new BaseSettingsCommand(
+            stateManager,
+            new PluginSettingsProvider(PluginSettings.from(Map.of())),
+            mock(BaseFlightController.class),
+            pocketBases
+        );
+
+        command.onCommand(player, null, "basesettings", new String[] {
+            "pocket", "type", "nether", "crimson_forest"
+        });
+
+        verify(pocketBases).setBiome(playerId, PocketBaseBiome.CRIMSON_FOREST);
+        verify(inventory).setStorageContents(any(ItemStack[].class));
+    }
+
+    @Test
+    void selectingCurrentPocketBiomeDoesNotCharge() throws Exception {
+        UUID playerId = UUID.randomUUID();
+        Player player = mock(Player.class);
+        when(player.getUniqueId()).thenReturn(playerId);
+        when(player.getName()).thenReturn("Builder");
+        PlayerInventory inventory = mock(PlayerInventory.class);
+        when(player.getInventory()).thenReturn(inventory);
         BaseStateManager stateManager = mock(BaseStateManager.class);
         when(stateManager.player(playerId, "Builder"))
             .thenReturn(PlayerState.newPlayer(playerId, "Builder"));
         PocketBaseManager pocketBases = mock(PocketBaseManager.class);
         when(pocketBases.state(playerId)).thenReturn(
-            new PocketBaseState(playerId, 1, java.util.Optional.empty(), false)
-        );
-        when(pocketBases.setMobSpawning(playerId, true)).thenReturn(
-            new PocketBaseState(playerId, 1, java.util.Optional.empty(), true)
+            new PocketBaseState(playerId, 1, java.util.Optional.empty())
         );
         BaseSettingsCommand command = new BaseSettingsCommand(
             stateManager,
@@ -232,13 +313,50 @@ final class BaseSettingsCommandTest {
             pocketBases
         );
 
-        command.onCommand(
-            player, null, "basesettings", new String[] {"pocket", "mobs", "enable"}
+        command.onCommand(player, null, "basesettings", new String[] {
+            "pocket", "type", "void", "the_void"
+        });
+
+        verify(pocketBases, never()).setBiome(
+            org.mockito.ArgumentMatchers.eq(playerId),
+            org.mockito.ArgumentMatchers.any(PocketBaseBiome.class)
+        );
+        verify(inventory, never()).setStorageContents(any(ItemStack[].class));
+    }
+
+    @Test
+    void pocketOwnerCanEnableHostileMobSpawningWithoutChangingPassive() throws Exception {
+        UUID playerId = UUID.randomUUID();
+        Player player = mock(Player.class);
+        when(player.getUniqueId()).thenReturn(playerId);
+        when(player.getName()).thenReturn("Builder");
+        BaseStateManager stateManager = mock(BaseStateManager.class);
+        when(stateManager.player(playerId, "Builder"))
+            .thenReturn(PlayerState.newPlayer(playerId, "Builder"));
+        PocketBaseManager pocketBases = mock(PocketBaseManager.class);
+        PocketBaseState current = new PocketBaseState(
+            playerId, 1, java.util.Optional.empty(), java.util.Optional.empty(),
+            false, true, PocketBaseBiome.THE_VOID
+        );
+        when(pocketBases.state(playerId)).thenReturn(current);
+        when(pocketBases.setHostileMobSpawning(playerId, true)).thenReturn(
+            current.withHostileMobSpawningEnabled(true)
+        );
+        BaseSettingsCommand command = new BaseSettingsCommand(
+            stateManager,
+            new PluginSettingsProvider(PluginSettings.from(Map.of())),
+            mock(BaseFlightController.class),
+            pocketBases
         );
 
-        verify(pocketBases).setMobSpawning(playerId, true);
+        command.onCommand(player, null, "basesettings", new String[] {
+            "pocket", "mobs", "hostile", "enable"
+        });
+
+        verify(pocketBases).setHostileMobSpawning(playerId, true);
+        verify(pocketBases, never()).setPassiveMobSpawning(playerId, true);
         verify(player).sendMessage(org.mockito.ArgumentMatchers.<String>argThat(
-            message -> message.contains("mob spawning") && message.contains("enabled")
+            message -> message.contains("hostile mob spawning") && message.contains("enabled")
         ));
     }
 
@@ -253,9 +371,9 @@ final class BaseSettingsCommandTest {
             .thenReturn(PlayerState.newPlayer(playerId, "Builder"));
         PocketBaseManager pocketBases = mock(PocketBaseManager.class);
         when(pocketBases.state(playerId)).thenReturn(
-            new PocketBaseState(playerId, 1, java.util.Optional.empty(), false)
+            new PocketBaseState(playerId, 1, java.util.Optional.empty())
         );
-        when(pocketBases.setMobSpawning(playerId, true))
+        when(pocketBases.setPassiveMobSpawning(playerId, true))
             .thenThrow(new IOException("save failed"));
         BaseSettingsCommand command = new BaseSettingsCommand(
             stateManager,
@@ -264,9 +382,9 @@ final class BaseSettingsCommandTest {
             pocketBases
         );
 
-        command.onCommand(
-            player, null, "basesettings", new String[] {"pocket", "mobs", "enable"}
-        );
+        command.onCommand(player, null, "basesettings", new String[] {
+            "pocket", "mobs", "passive", "enable"
+        });
 
         verify(player).sendMessage(org.mockito.ArgumentMatchers.<String>argThat(
             message -> message.contains("could not be changed")
@@ -294,11 +412,11 @@ final class BaseSettingsCommandTest {
             pocketBases
         );
 
-        command.onCommand(
-            player, null, "basesettings", new String[] {"pocket", "mobs", "enable"}
-        );
+        command.onCommand(player, null, "basesettings", new String[] {
+            "pocket", "mobs", "hostile", "enable"
+        });
 
-        verify(pocketBases, never()).setMobSpawning(playerId, true);
+        verify(pocketBases, never()).setHostileMobSpawning(playerId, true);
         verify(player).sendMessage(org.mockito.ArgumentMatchers.<String>argThat(
             message -> message.contains("Pocket Base I") && message.contains("locked")
         ));
@@ -311,10 +429,9 @@ final class BaseSettingsCommandTest {
         when(player.getUniqueId()).thenReturn(playerId);
         when(player.getName()).thenReturn("Builder");
         PlayerInventory inventory = mock(PlayerInventory.class);
+        ItemStack currency = item(Material.DIAMOND_BLOCK, 64);
         when(player.getInventory()).thenReturn(inventory);
-        when(inventory.getStorageContents()).thenReturn(new ItemStack[] {
-            new ItemStack(Material.DIAMOND_BLOCK, 64)
-        });
+        when(inventory.getStorageContents()).thenReturn(new ItemStack[] {currency});
         PlayerState owner = PlayerState.newPlayer(playerId, "Builder")
             .withAdministrativeLevels(4, 0, 0, 0, 0, false, false, true)
             .withBase(
@@ -343,7 +460,7 @@ final class BaseSettingsCommandTest {
     }
 
     @Test
-    void statusDisplaysPocketMobSpawningPreference() {
+    void statusDisplaysPocketMobSpawningPreferences() {
         UUID playerId = UUID.randomUUID();
         Player player = mock(Player.class);
         when(player.getUniqueId()).thenReturn(playerId);
@@ -353,7 +470,10 @@ final class BaseSettingsCommandTest {
             .thenReturn(PlayerState.newPlayer(playerId, "Builder"));
         PocketBaseManager pocketBases = mock(PocketBaseManager.class);
         when(pocketBases.state(playerId)).thenReturn(
-            new PocketBaseState(playerId, 1, java.util.Optional.empty(), false)
+            new PocketBaseState(
+                playerId, 1, java.util.Optional.empty(), java.util.Optional.empty(),
+                true, false, PocketBaseBiome.THE_VOID
+            )
         );
         BaseSettingsCommand command = new BaseSettingsCommand(
             stateManager,
@@ -366,7 +486,9 @@ final class BaseSettingsCommandTest {
 
         verify(player).sendMessage(org.mockito.ArgumentMatchers.<String>argThat(
             message -> message.contains("Pocket Base 1")
-                && message.contains("mob spawning=disabled")
+                && message.contains("type=void/the_void")
+                && message.contains("hostile spawning=enabled")
+                && message.contains("passive spawning=disabled")
         ));
     }
 
@@ -419,7 +541,7 @@ final class BaseSettingsCommandTest {
     }
 
     @Test
-    void defaultAndStatusDisplayTheFullProgressReport() {
+    void defaultAndUiOpenDialogWhileStatusDisplaysTheFullProgressReport() {
         UUID playerId = UUID.randomUUID();
         Player player = mock(Player.class);
         when(player.getUniqueId()).thenReturn(playerId);
@@ -431,21 +553,25 @@ final class BaseSettingsCommandTest {
         BaseSettingsCommand command = new BaseSettingsCommand(
             stateManager,
             new PluginSettingsProvider(PluginSettings.from(Map.of())),
-            mock(BaseFlightController.class)
+            mock(BaseFlightController.class),
+            null,
+            (owner, pocket) -> null
         );
 
         command.onCommand(player, null, "basesettings", new String[0]);
+        command.onCommand(player, null, "homesettings", new String[] {"ui"});
         command.onCommand(player, null, "basesettings", new String[] {"status"});
 
-        verify(player, times(2)).sendMessage(ChatColor.GOLD + "=== Base Progress ===");
-        verify(player, times(2)).sendMessage(
+        verify(player, times(2)).showDialog((DialogLike) null);
+        verify(player).sendMessage(ChatColor.GOLD + "=== Base Progress ===");
+        verify(player).sendMessage(
             org.mockito.ArgumentMatchers.<String>argThat(message ->
                 message.contains("Spawnable Overlay:")
                     && message.contains("0/250 placements")
                     && message.contains("locked")
             )
         );
-        verify(player, times(2)).sendMessage(
+        verify(player).sendMessage(
             org.mockito.ArgumentMatchers.<String>argThat(message ->
             message.contains("Settings: visitors=")
                 && message.contains("navigation=")
@@ -457,6 +583,18 @@ final class BaseSettingsCommandTest {
         );
     }
 
+    private static ItemStack item(Material material, int amount) {
+        ItemStack item = mock(ItemStack.class);
+        ItemStack copy = mock(ItemStack.class);
+        when(item.getType()).thenReturn(material);
+        when(item.getAmount()).thenReturn(amount);
+        when(item.clone()).thenReturn(copy);
+        when(copy.getType()).thenReturn(material);
+        when(copy.getAmount()).thenReturn(amount);
+        when(copy.clone()).thenReturn(copy);
+        return item;
+    }
+
     private static CommandResult execute(PlayerState current, String... arguments) {
         Player player = mock(Player.class);
         when(player.getUniqueId()).thenReturn(current.playerId());

src/test/java/games/dmg/spigotbase/BaseSettingsDialogFactoryTest.java

@@ -0,0 +1,152 @@
+package games.dmg.spigotbase;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertInstanceOf;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.time.Instant;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.UUID;
+import net.kyori.adventure.text.event.ClickEvent;
+import org.junit.jupiter.api.Test;
+
+final class BaseSettingsDialogFactoryTest {
+    @Test
+    void createsStaticRunCommandActionWithoutMacroVariables() {
+        ClickEvent<ClickEvent.Payload.Text> action = BaseSettingsDialogFactory.commandClick(
+            "/basesettings status"
+        );
+
+        assertEquals(ClickEvent.Action.RUN_COMMAND, action.action());
+        ClickEvent.Payload.Text payload = assertInstanceOf(
+            ClickEvent.Payload.Text.class,
+            action.payload()
+        );
+        assertEquals("/basesettings status", payload.value());
+    }
+
+    @Test
+    void createsControlsForEveryBaseSettingAndConfirmedPurchase() {
+        UUID playerId = UUID.randomUUID();
+        PlayerState owner = PlayerState.newPlayer(playerId, "Builder")
+            .withAdministrativeLevels(4, 2, 2, 1, 1, true, true, true)
+            .withBase(
+                new BaseLocation(UUID.randomUUID(), "world", 10, 64, 20, 10, 20),
+                Instant.EPOCH
+            )
+            .withBorderEnabled(true)
+            .withTotalBlocksPlaced(250)
+            .withSpawnableOverlayEnabled(true);
+        PocketBaseState pocket = new PocketBaseState(
+            playerId,
+            1,
+            Optional.empty(),
+            Optional.empty(),
+            true,
+            false,
+            PocketBaseBiome.PLAINS
+        );
+
+        BaseSettingsDialogFactory.DialogSpec specification =
+            new BaseSettingsDialogFactory(PluginSettings.from(Map.of()))
+                .specification(owner, pocket);
+
+        BaseSettingsDialogFactory.ListSpec root = assertInstanceOf(
+            BaseSettingsDialogFactory.ListSpec.class,
+            specification
+        );
+        assertTrue(root.content().message().contains("Base 4/4"));
+        List<String> commands = commands(root);
+        assertTrue(commands.contains("/basesettings status"));
+        assertTrue(commands.contains("/basesettings visitors blocked"));
+        assertTrue(commands.contains("/basesettings navigation disable"));
+        assertTrue(commands.contains("/basesettings flight disable"));
+        assertTrue(commands.contains("/basesettings border disable"));
+        assertTrue(commands.contains("/basesettings spawnable disable"));
+        assertTrue(commands.contains("/basesettings bossbar disable"));
+        assertTrue(commands.contains("/basesettings pocket upgrade"));
+        assertTrue(commands.contains("/basesettings pocket mobs hostile disable"));
+        assertTrue(commands.contains("/basesettings pocket mobs passive enable"));
+        assertTrue(commands.contains("/basesettings pocket type nether crimson_forest"));
+    }
+
+    @Test
+    void requiresConfirmationForBaseIvPurchase() {
+        UUID playerId = UUID.randomUUID();
+        PlayerState owner = PlayerState.newPlayer(playerId, "Builder")
+            .withAdministrativeLevels(3, 0, 0, 0, 0, false, false, false)
+            .withBase(
+                new BaseLocation(UUID.randomUUID(), "world", 0, 64, 0, 0, 0),
+                Instant.EPOCH
+            );
+
+        BaseSettingsDialogFactory.ListSpec root = assertInstanceOf(
+            BaseSettingsDialogFactory.ListSpec.class,
+            new BaseSettingsDialogFactory(PluginSettings.from(Map.of())).specification(
+                owner,
+                PocketBaseState.locked(playerId)
+            )
+        );
+        BaseSettingsDialogFactory.ConfirmationSpec upgrade = assertInstanceOf(
+            BaseSettingsDialogFactory.ConfirmationSpec.class,
+            root.dialogs().get(2)
+        );
+
+        assertEquals("/basesettings upgrade", upgrade.confirm().command());
+    }
+
+    @Test
+    void marksUnavailableControlsAsLocked() {
+        UUID playerId = UUID.randomUUID();
+        PlayerState owner = PlayerState.newPlayer(playerId, "Newcomer");
+
+        BaseSettingsDialogFactory.ListSpec root = assertInstanceOf(
+            BaseSettingsDialogFactory.ListSpec.class,
+            new BaseSettingsDialogFactory(PluginSettings.from(Map.of())).specification(
+                owner,
+                PocketBaseState.locked(playerId)
+            )
+        );
+        BaseSettingsDialogFactory.MultiSpec controls = assertInstanceOf(
+            BaseSettingsDialogFactory.MultiSpec.class,
+            root.dialogs().get(0)
+        );
+        List<String> labels = controls.actions().stream()
+            .map(BaseSettingsDialogFactory.ButtonSpec::label)
+            .toList();
+
+        assertTrue(labels.stream().anyMatch(label -> label.contains("Visitors: Locked")));
+        assertTrue(labels.stream().anyMatch(label -> label.contains("Navigation: Locked")));
+        assertTrue(labels.stream().anyMatch(label -> label.contains("Flight: Locked")));
+        assertTrue(labels.stream().anyMatch(label -> label.contains("Border: Locked")));
+        assertTrue(labels.stream().anyMatch(label -> label.contains("Spawnable Overlay: Locked")));
+    }
+
+    private static List<String> commands(
+        BaseSettingsDialogFactory.DialogSpec specification
+    ) {
+        List<String> commands = new ArrayList<>();
+        collect(specification, commands);
+        return commands;
+    }
+
+    private static void collect(
+        BaseSettingsDialogFactory.DialogSpec specification,
+        List<String> commands
+    ) {
+        if (specification instanceof BaseSettingsDialogFactory.ListSpec list) {
+            list.dialogs().forEach(child -> collect(child, commands));
+        } else if (specification instanceof BaseSettingsDialogFactory.MultiSpec multi) {
+            multi.actions().forEach(button -> commands.add(button.command()));
+        } else if (specification
+                instanceof BaseSettingsDialogFactory.ConfirmationSpec confirmation) {
+            commands.add(confirmation.confirm().command());
+        } else if (specification instanceof BaseSettingsDialogFactory.NoticeSpec notice
+                && notice.action() != null) {
+            commands.add(notice.action().command());
+        }
+    }
+}

src/test/java/games/dmg/spigotbase/PluginSettingsTest.java

@@ -25,6 +25,8 @@ final class PluginSettingsTest {
         assertEquals(16, settings.pocketBaseUpgradeCost());
         assertEquals("DIAMOND_BLOCK", settings.pocketBaseCurrencyMaterial());
         assertEquals("DIAMOND_BLOCK", settings.pocketBasePortalFrameMaterial());
+        assertEquals(16, settings.pocketBaseBiomeChangeCost());
+        assertEquals("NETHERITE_BLOCK", settings.pocketBaseBiomeCurrencyMaterial());
     }
 
     @Test
@@ -33,13 +35,17 @@ final class PluginSettingsTest {
             "pocket-base-unlock-cost", 32,
             "pocket-base-upgrade-cost", 8,
             "pocket-base-currency-material", "EMERALD_BLOCK",
-            "pocket-base-portal-frame-material", "GOLD_BLOCK"
+            "pocket-base-portal-frame-material", "GOLD_BLOCK",
+            "pocket-base-biome-change-cost", 12,
+            "pocket-base-biome-currency-material", "NETHERITE_INGOT"
         ));
 
         assertEquals(32, settings.pocketBaseUnlockCost());
         assertEquals(8, settings.pocketBaseUpgradeCost());
         assertEquals("EMERALD_BLOCK", settings.pocketBaseCurrencyMaterial());
         assertEquals("GOLD_BLOCK", settings.pocketBasePortalFrameMaterial());
+        assertEquals(12, settings.pocketBaseBiomeChangeCost());
+        assertEquals("NETHERITE_INGOT", settings.pocketBaseBiomeCurrencyMaterial());
     }
 
     @Test

src/test/java/games/dmg/spigotbase/PocketBaseControllerTest.java

@@ -1,5 +1,6 @@
 package games.dmg.spigotbase;
 
+import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.never;
@@ -8,20 +9,27 @@ import static org.mockito.Mockito.when;
 
 import java.time.Instant;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
 import java.util.UUID;
 import java.util.logging.Logger;
+import org.bukkit.Location;
 import org.bukkit.Material;
 import org.bukkit.Server;
 import org.bukkit.World;
 import org.bukkit.block.Block;
+import org.bukkit.entity.Entity;
+import org.bukkit.entity.Mob;
 import org.bukkit.entity.Player;
 import org.bukkit.event.block.Action;
 import org.bukkit.event.block.BlockPlaceEvent;
 import org.bukkit.event.player.PlayerInteractEvent;
+import org.bukkit.event.player.PlayerMoveEvent;
+import org.bukkit.event.player.PlayerTeleportEvent;
 import org.bukkit.inventory.ItemStack;
+import org.bukkit.util.BoundingBox;
 import org.junit.jupiter.api.Test;
 
 final class PocketBaseControllerTest {
@@ -37,6 +45,7 @@ final class PocketBaseControllerTest {
         World world = mock(World.class);
         Block clicked = block(world, -2, 66, 0, Material.DIAMOND_BLOCK);
         PlayerInteractEvent event = mock(PlayerInteractEvent.class);
+        ItemStack activator = item(Material.FLINT_AND_STEEL);
         BaseStateManager baseStates = mock(BaseStateManager.class);
         PocketBaseManager pocketBases = mock(PocketBaseManager.class);
         PluginSettings settings = PluginSettings.from(Map.of());
@@ -49,7 +58,7 @@ final class PocketBaseControllerTest {
         when(event.getPlayer()).thenReturn(owner);
         when(event.getAction()).thenReturn(Action.RIGHT_CLICK_BLOCK);
         when(event.getClickedBlock()).thenReturn(clicked);
-        when(event.getItem()).thenReturn(new ItemStack(Material.FLINT_AND_STEEL));
+        when(event.getItem()).thenReturn(activator);
         when(world.getUID()).thenReturn(worldId);
         when(world.getName()).thenReturn("world");
         when(world.getBlockAt(anyInt(), anyInt(), anyInt())).thenAnswer(invocation -> {
@@ -98,6 +107,7 @@ final class PocketBaseControllerTest {
         World world = mock(World.class);
         Block clicked = block(world, 8, 67, 8, Material.DIAMOND_BLOCK);
         PlayerInteractEvent event = mock(PlayerInteractEvent.class);
+        ItemStack activator = item(Material.FLINT_AND_STEEL);
         PocketBaseManager pocketBases = mock(PocketBaseManager.class);
         PluginSettings settings = PluginSettings.from(Map.of());
 
@@ -105,7 +115,7 @@ final class PocketBaseControllerTest {
         when(event.getPlayer()).thenReturn(owner);
         when(event.getAction()).thenReturn(Action.RIGHT_CLICK_BLOCK);
         when(event.getClickedBlock()).thenReturn(clicked);
-        when(event.getItem()).thenReturn(new ItemStack(Material.FLINT_AND_STEEL));
+        when(event.getItem()).thenReturn(activator);
         when(world.getUID()).thenReturn(worldId);
         when(world.getName()).thenReturn("pocket");
         when(world.getBlockAt(anyInt(), anyInt(), anyInt())).thenAnswer(invocation -> {
@@ -152,6 +162,7 @@ final class PocketBaseControllerTest {
         World world = mock(World.class);
         Block clicked = block(world, 30, 67, 8, Material.DIAMOND_BLOCK);
         PlayerInteractEvent event = mock(PlayerInteractEvent.class);
+        ItemStack activator = item(Material.FLINT_AND_STEEL);
         PocketBaseManager pocketBases = mock(PocketBaseManager.class);
         PluginSettings settings = PluginSettings.from(Map.of());
 
@@ -159,7 +170,7 @@ final class PocketBaseControllerTest {
         when(event.getPlayer()).thenReturn(owner);
         when(event.getAction()).thenReturn(Action.RIGHT_CLICK_BLOCK);
         when(event.getClickedBlock()).thenReturn(clicked);
-        when(event.getItem()).thenReturn(new ItemStack(Material.FLINT_AND_STEEL));
+        when(event.getItem()).thenReturn(activator);
         when(world.getUID()).thenReturn(worldId);
         when(world.getName()).thenReturn("pocket");
         when(world.getBlockAt(anyInt(), anyInt(), anyInt())).thenAnswer(invocation -> {
@@ -227,6 +238,188 @@ final class PocketBaseControllerTest {
         verify(event).setCancelled(true);
     }
 
+    @Test
+    void activeEntranceTransportsMobsOnceButNotOtherEntities() {
+        UUID ownerId = UUID.randomUUID();
+        UUID worldId = UUID.randomUUID();
+        PocketPortalLocation portal = new PocketPortalLocation(
+            worldId, "world", -2, 64, 0, PocketPortalAxis.X
+        );
+        PocketBaseState state = new PocketBaseState(ownerId, 1, Optional.of(portal));
+        Server server = mock(Server.class);
+        World world = intactPortalWorld(worldId, portal);
+        Mob mob = mock(Mob.class);
+        Entity item = mock(Entity.class);
+        Location arrival = new Location(mock(World.class), 0.5, 65.0, 5.5);
+        PocketBaseManager pocketBases = mock(PocketBaseManager.class);
+
+        when(mob.getUniqueId()).thenReturn(UUID.randomUUID());
+        when(item.getUniqueId()).thenReturn(UUID.randomUUID());
+        when(world.getNearbyEntities(any(BoundingBox.class), any()))
+            .thenReturn(List.of(mob, item));
+        when(server.getWorld(worldId)).thenReturn(world);
+        when(pocketBases.knownStates()).thenReturn(Map.of(ownerId, state));
+        when(pocketBases.pocketArrival(ownerId)).thenReturn(arrival);
+        PocketBaseController controller = controller(server, pocketBases);
+
+        controller.scanMobPortals();
+        controller.scanMobPortals();
+
+        verify(mob).teleport(arrival, PlayerTeleportEvent.TeleportCause.PLUGIN);
+        verify(item, never()).teleport(
+            any(Location.class),
+            any(PlayerTeleportEvent.TeleportCause.class)
+        );
+    }
+
+    @Test
+    void activeReturnPortalTransportsMobOutsideIntactEntrance() {
+        UUID ownerId = UUID.randomUUID();
+        UUID normalWorldId = UUID.randomUUID();
+        UUID pocketWorldId = UUID.randomUUID();
+        PocketPortalLocation entrance = new PocketPortalLocation(
+            normalWorldId, "world", -2, 64, 0, PocketPortalAxis.X
+        );
+        PocketPortalLocation returnPortal = new PocketPortalLocation(
+            pocketWorldId, "pocket", 8, 65, 8, PocketPortalAxis.Z
+        );
+        PocketBaseState state = new PocketBaseState(ownerId, 1, Optional.of(entrance));
+        Server server = mock(Server.class);
+        World normalWorld = intactPortalWorld(normalWorldId, entrance);
+        World pocketWorld = intactPortalWorld(pocketWorldId, returnPortal);
+        Mob mob = mock(Mob.class);
+        PocketBaseManager pocketBases = mock(PocketBaseManager.class);
+
+        when(mob.getUniqueId()).thenReturn(UUID.randomUUID());
+        when(normalWorld.getNearbyEntities(any(BoundingBox.class), any()))
+            .thenReturn(List.of());
+        when(pocketWorld.getNearbyEntities(any(BoundingBox.class), any()))
+            .thenReturn(List.of(mob));
+        when(server.getWorld(normalWorldId)).thenReturn(normalWorld);
+        when(server.getWorld(pocketWorldId)).thenReturn(pocketWorld);
+        when(pocketBases.knownStates()).thenReturn(Map.of(ownerId, state));
+        when(pocketBases.state(ownerId)).thenReturn(state);
+        when(pocketBases.returnPortalIsIntact(ownerId)).thenReturn(true);
+        when(pocketBases.returnPortal(ownerId)).thenReturn(returnPortal);
+        PocketBaseController controller = controller(server, pocketBases);
+
+        controller.scanMobPortals();
+
+        verify(mob).teleport(
+            new Location(normalWorld, 0.0, 65.0, 1.5),
+            PlayerTeleportEvent.TeleportCause.PLUGIN
+        );
+    }
+
+    @Test
+    void voidReturnClearsAccumulatedPlayerFallDistance() {
+        UUID ownerId = UUID.randomUUID();
+        UUID pocketWorldId = UUID.randomUUID();
+        World pocketWorld = mock(World.class);
+        World fallbackWorld = mock(World.class);
+        Location destination = new Location(pocketWorld, 0.5, -65.0, 0.5);
+        Location spawn = new Location(fallbackWorld, 10.5, 70.0, 10.5);
+        Player player = mock(Player.class);
+        PlayerMoveEvent event = mock(PlayerMoveEvent.class);
+        PocketBaseManager pocketBases = mock(PocketBaseManager.class);
+        Server server = mock(Server.class);
+
+        when(pocketWorld.getUID()).thenReturn(pocketWorldId);
+        when(player.getUniqueId()).thenReturn(UUID.randomUUID());
+        when(event.getPlayer()).thenReturn(player);
+        when(event.getTo()).thenReturn(destination);
+        when(server.getWorlds()).thenReturn(List.of(fallbackWorld));
+        when(fallbackWorld.getSpawnLocation()).thenReturn(spawn);
+        when(pocketBases.ownerForPocketWorld(pocketWorldId)).thenReturn(Optional.of(ownerId));
+        when(pocketBases.state(ownerId)).thenReturn(
+            new PocketBaseState(ownerId, 1, Optional.empty())
+        );
+        PocketBaseController controller = controller(server, pocketBases);
+
+        controller.onMove(event);
+
+        verify(player).setFallDistance(0.0F);
+        verify(player).teleport(spawn, PlayerTeleportEvent.TeleportCause.PLUGIN);
+    }
+
+    @Test
+    void mobReturnFallsBackToServerSpawnWithoutValidEntrance() {
+        UUID ownerId = UUID.randomUUID();
+        UUID pocketWorldId = UUID.randomUUID();
+        PocketPortalLocation returnPortal = new PocketPortalLocation(
+            pocketWorldId, "pocket", 8, 65, 8, PocketPortalAxis.Z
+        );
+        PocketBaseState state = new PocketBaseState(ownerId, 1, Optional.empty());
+        Server server = mock(Server.class);
+        World pocketWorld = intactPortalWorld(pocketWorldId, returnPortal);
+        World fallbackWorld = mock(World.class);
+        Location spawn = new Location(fallbackWorld, 10.5, 70.0, 10.5);
+        Mob mob = mock(Mob.class);
+        PocketBaseManager pocketBases = mock(PocketBaseManager.class);
+
+        when(mob.getUniqueId()).thenReturn(UUID.randomUUID());
+        when(pocketWorld.getNearbyEntities(any(BoundingBox.class), any()))
+            .thenReturn(List.of(mob));
+        when(server.getWorld(pocketWorldId)).thenReturn(pocketWorld);
+        when(server.getWorlds()).thenReturn(List.of(fallbackWorld));
+        when(fallbackWorld.getSpawnLocation()).thenReturn(spawn);
+        when(pocketBases.knownStates()).thenReturn(Map.of(ownerId, state));
+        when(pocketBases.state(ownerId)).thenReturn(state);
+        when(pocketBases.returnPortalIsIntact(ownerId)).thenReturn(true);
+        when(pocketBases.returnPortal(ownerId)).thenReturn(returnPortal);
+        PocketBaseController controller = controller(server, pocketBases);
+
+        controller.scanMobPortals();
+
+        verify(mob).teleport(
+            spawn,
+            PlayerTeleportEvent.TeleportCause.PLUGIN
+        );
+    }
+
+    private static PocketBaseController controller(
+        Server server,
+        PocketBaseManager pocketBases
+    ) {
+        PluginSettings settings = PluginSettings.from(Map.of());
+        return new PocketBaseController(
+            server,
+            mock(BaseStateManager.class),
+            new BaseBoundsService(settings),
+            pocketBases,
+            new PluginSettingsProvider(settings),
+            Logger.getAnonymousLogger()
+        );
+    }
+
+    private static World intactPortalWorld(
+        UUID worldId,
+        PocketPortalLocation portal
+    ) {
+        World world = mock(World.class);
+        Set<BlockPosition> frame = new HashSet<>(PocketPortalGeometry.frameBlocks(portal));
+        when(world.getUID()).thenReturn(worldId);
+        when(world.getBlockAt(anyInt(), anyInt(), anyInt())).thenAnswer(invocation -> {
+            BlockPosition position = new BlockPosition(
+                invocation.getArgument(0), invocation.getArgument(1), invocation.getArgument(2)
+            );
+            return block(
+                world,
+                position.x(),
+                position.y(),
+                position.z(),
+                frame.contains(position) ? Material.DIAMOND_BLOCK : Material.AIR
+            );
+        });
+        return world;
+    }
+
+    private static ItemStack item(Material material) {
+        ItemStack item = mock(ItemStack.class);
+        when(item.getType()).thenReturn(material);
+        return item;
+    }
+
     private static Block block(
         World world,
         int x,

src/test/java/games/dmg/spigotbase/PocketBaseManagerTest.java

@@ -25,7 +25,8 @@ final class PocketBaseManagerTest {
         PocketBaseStateManager states = mock(PocketBaseStateManager.class);
         PocketBaseWorldService worlds = mock(PocketBaseWorldService.class);
         when(states.state(ownerId)).thenReturn(new PocketBaseState(
-            ownerId, 1, Optional.empty(), Optional.of(relocated), false
+            ownerId, 1, Optional.empty(), Optional.of(relocated), false, false,
+            PocketBaseBiome.THE_VOID
         ));
         PocketBaseManager manager = new PocketBaseManager(
             states,
@@ -58,9 +59,12 @@ final class PocketBaseManagerTest {
     }
 
     @Test
-    void persistsAndAppliesMobSpawningPreference() throws Exception {
+    void persistsAndAppliesHostileMobSpawningWithoutChangingPassive() throws Exception {
         UUID ownerId = UUID.randomUUID();
-        PocketBaseState current = new PocketBaseState(ownerId, 1, Optional.empty(), false);
+        PocketBaseState current = new PocketBaseState(
+            ownerId, 1, Optional.empty(), Optional.empty(), false, true,
+            PocketBaseBiome.THE_VOID
+        );
         PocketBaseStateManager states = mock(PocketBaseStateManager.class);
         PocketBaseWorldService worlds = mock(PocketBaseWorldService.class);
         when(states.state(ownerId)).thenReturn(current);
@@ -76,19 +80,50 @@ final class PocketBaseManagerTest {
             new PluginSettingsProvider(PluginSettings.from(Map.of()))
         );
 
-        manager.setMobSpawning(ownerId, true);
+        PocketBaseState updated = manager.setHostileMobSpawning(ownerId, true);
 
+        assertEquals(true, updated.hostileMobSpawningEnabled());
+        assertEquals(true, updated.passiveMobSpawningEnabled());
         InOrder order = inOrder(worlds, states);
-        order.verify(worlds).setMobSpawning(ownerId, true);
+        order.verify(worlds).setMobSpawning(ownerId, true, true);
         order.verify(states).updateAndSave(
             org.mockito.ArgumentMatchers.eq(ownerId), org.mockito.ArgumentMatchers.any()
         );
     }
 
     @Test
-    void restoresWorldSettingWhenPersistenceFails() throws Exception {
+    void persistsBiomeAfterApplyingItToTheUnlockedArea() throws Exception {
         UUID ownerId = UUID.randomUUID();
-        PocketBaseState current = new PocketBaseState(ownerId, 1, Optional.empty(), false);
+        PocketBaseState current = new PocketBaseState(ownerId, 2, Optional.empty());
+        PocketBaseStateManager states = mock(PocketBaseStateManager.class);
+        PocketBaseWorldService worlds = mock(PocketBaseWorldService.class);
+        when(states.state(ownerId)).thenReturn(current);
+        when(states.updateAndSave(org.mockito.ArgumentMatchers.eq(ownerId),
+            org.mockito.ArgumentMatchers.any())).thenAnswer(invocation -> {
+                @SuppressWarnings("unchecked")
+                UnaryOperator<PocketBaseState> operation = invocation.getArgument(1);
+                return operation.apply(current);
+            });
+        PocketBaseManager manager = new PocketBaseManager(
+            states,
+            worlds,
+            new PluginSettingsProvider(PluginSettings.from(Map.of()))
+        );
+
+        PocketBaseState updated = manager.setBiome(ownerId, PocketBaseBiome.WARPED_FOREST);
+
+        assertEquals(PocketBaseBiome.WARPED_FOREST, updated.biome());
+        InOrder order = inOrder(worlds, states);
+        order.verify(worlds).setBiome(ownerId, 2, PocketBaseBiome.WARPED_FOREST);
+        order.verify(states).updateAndSave(
+            org.mockito.ArgumentMatchers.eq(ownerId), org.mockito.ArgumentMatchers.any()
+        );
+    }
+
+    @Test
+    void restoresPreviousBiomeWhenPersistenceFails() throws Exception {
+        UUID ownerId = UUID.randomUUID();
+        PocketBaseState current = new PocketBaseState(ownerId, 1, Optional.empty());
         PocketBaseStateManager states = mock(PocketBaseStateManager.class);
         PocketBaseWorldService worlds = mock(PocketBaseWorldService.class);
         when(states.state(ownerId)).thenReturn(current);
@@ -100,9 +135,35 @@ final class PocketBaseManagerTest {
             new PluginSettingsProvider(PluginSettings.from(Map.of()))
         );
 
-        assertThrows(IOException.class, () -> manager.setMobSpawning(ownerId, true));
+        assertThrows(IOException.class,
+            () -> manager.setBiome(ownerId, PocketBaseBiome.DESERT));
 
-        verify(worlds).setMobSpawning(ownerId, true);
-        verify(worlds).setMobSpawning(ownerId, false);
+        verify(worlds).setBiome(ownerId, 1, PocketBaseBiome.DESERT);
+        verify(worlds).setBiome(ownerId, 1, PocketBaseBiome.THE_VOID);
+    }
+
+    @Test
+    void restoresBothWorldSettingsWhenPersistenceFails() throws Exception {
+        UUID ownerId = UUID.randomUUID();
+        PocketBaseState current = new PocketBaseState(
+            ownerId, 1, Optional.empty(), Optional.empty(), true, false,
+            PocketBaseBiome.THE_VOID
+        );
+        PocketBaseStateManager states = mock(PocketBaseStateManager.class);
+        PocketBaseWorldService worlds = mock(PocketBaseWorldService.class);
+        when(states.state(ownerId)).thenReturn(current);
+        when(states.updateAndSave(org.mockito.ArgumentMatchers.eq(ownerId),
+            org.mockito.ArgumentMatchers.any())).thenThrow(new IOException("save failed"));
+        PocketBaseManager manager = new PocketBaseManager(
+            states,
+            worlds,
+            new PluginSettingsProvider(PluginSettings.from(Map.of()))
+        );
+
+        assertThrows(IOException.class,
+            () -> manager.setPassiveMobSpawning(ownerId, true));
+
+        verify(worlds).setMobSpawning(ownerId, true, true);
+        verify(worlds).setMobSpawning(ownerId, true, false);
     }
 }

src/test/java/games/dmg/spigotbase/PocketBaseWorldServiceTest.java

@@ -31,9 +31,12 @@ final class PocketBaseWorldServiceTest {
         when(server.createWorld(any(WorldCreator.class))).thenReturn(world);
         when(world.getUID()).thenReturn(worldId);
         when(world.getName()).thenReturn("pocket");
+        when(world.getMinHeight()).thenReturn(0);
+        when(world.getMaxHeight()).thenReturn(8);
         PocketBaseWorldService service = new PocketBaseWorldService(
             server,
-            new PluginSettingsProvider(PluginSettings.from(Map.of()))
+            new PluginSettingsProvider(PluginSettings.from(Map.of())),
+            ignored -> null
         );
 
         service.expand(ownerId, 0, 1);
@@ -84,15 +87,45 @@ final class PocketBaseWorldServiceTest {
         when(world.getUID()).thenReturn(UUID.randomUUID());
         PocketBaseWorldService service = new PocketBaseWorldService(
             server,
-            new PluginSettingsProvider(PluginSettings.from(Map.of()))
+            new PluginSettingsProvider(PluginSettings.from(Map.of())),
+            ignored -> null
         );
 
         service.loadExisting(Map.of(
             ownerId,
-            new PocketBaseState(ownerId, 1, Optional.empty(), true)
+            new PocketBaseState(
+                ownerId, 1, Optional.empty(), Optional.empty(), true, false,
+                PocketBaseBiome.THE_VOID
+            )
         ));
 
-        verify(world).setSpawnFlags(true, true);
+        verify(world).setSpawnFlags(true, false);
+    }
+
+    @Test
+    void appliesSelectedBiomeAcrossUnlockedColumnsWithoutChangingBlocks() {
+        UUID ownerId = UUID.randomUUID();
+        Server server = mock(Server.class);
+        World world = mock(World.class);
+        when(server.getWorld(org.mockito.ArgumentMatchers.anyString())).thenReturn(world);
+        when(world.getUID()).thenReturn(UUID.randomUUID());
+        when(world.getMinHeight()).thenReturn(0);
+        when(world.getMaxHeight()).thenReturn(8);
+        PocketBaseWorldService service = new PocketBaseWorldService(
+            server,
+            new PluginSettingsProvider(PluginSettings.from(Map.of())),
+            ignored -> null
+        );
+
+        service.setBiome(ownerId, 1, PocketBaseBiome.CRIMSON_FOREST);
+
+        verify(world).setBiome(-32, 0, -32, null);
+        verify(world).setBiome(28, 4, 28, null);
+        verify(world, never()).getBlockAt(
+            org.mockito.ArgumentMatchers.anyInt(),
+            org.mockito.ArgumentMatchers.anyInt(),
+            org.mockito.ArgumentMatchers.anyInt()
+        );
     }
 
     @Test
@@ -104,9 +137,12 @@ final class PocketBaseWorldServiceTest {
         when(server.createWorld(any(WorldCreator.class))).thenReturn(world);
         when(world.getUID()).thenReturn(UUID.randomUUID());
         when(world.getName()).thenReturn("pocket");
+        when(world.getMinHeight()).thenReturn(0);
+        when(world.getMaxHeight()).thenReturn(8);
         PocketBaseWorldService service = new PocketBaseWorldService(
             server,
-            new PluginSettingsProvider(PluginSettings.from(Map.of()))
+            new PluginSettingsProvider(PluginSettings.from(Map.of())),
+            ignored -> null
         );
         Block existingCenter = world.getBlockAt(0, 64, 0);
 
@@ -116,6 +152,8 @@ final class PocketBaseWorldServiceTest {
             .setType(Material.GRASS_BLOCK, false);
         verify(existingCenter, never())
             .setType(any(Material.class), org.mockito.ArgumentMatchers.anyBoolean());
+        verify(world).setBiome(44, 4, 44, null);
+        verify(world, never()).setBiome(0, 0, 0, null);
     }
 
     private static Map<BlockPosition, Block> blocks(World world) {

src/test/java/games/dmg/spigotbase/YamlPocketBaseRepositoryTest.java

@@ -29,7 +29,9 @@ final class YamlPocketBaseRepositoryTest {
             Optional.of(new PocketPortalLocation(
                 worldId, "pocket", 20, 65, 12, PocketPortalAxis.Z
             )),
-            true
+            true,
+            false,
+            PocketBaseBiome.CRIMSON_FOREST
         );
         YamlPocketBaseRepository repository = new YamlPocketBaseRepository(
             temporaryDirectory.resolve("pocket-bases.yml")
@@ -49,7 +51,23 @@ final class YamlPocketBaseRepositoryTest {
 
         PocketBaseState loaded = repository.load().get(ownerId);
 
-        assertFalse(loaded.mobSpawningEnabled());
+        assertFalse(loaded.hostileMobSpawningEnabled());
+        assertFalse(loaded.passiveMobSpawningEnabled());
         assertTrue(loaded.returnPortal().isEmpty());
+        assertEquals(PocketBaseBiome.THE_VOID, loaded.biome());
+    }
+
+    @Test
+    void migratesLegacyMobPreferenceToBothCategories() throws Exception {
+        UUID ownerId = UUID.randomUUID();
+        Path stateFile = temporaryDirectory.resolve("pocket-bases.yml");
+        Files.writeString(stateFile, "owners:\n  " + ownerId
+            + ":\n    level: 1\n    mob-spawning-enabled: true\n");
+        YamlPocketBaseRepository repository = new YamlPocketBaseRepository(stateFile);
+
+        PocketBaseState loaded = repository.load().get(ownerId);
+
+        assertTrue(loaded.hostileMobSpawningEnabled());
+        assertTrue(loaded.passiveMobSpawningEnabled());
     }
 }