✨ implement unified tile system (Issue #14)

- Tree seedlings: plant tree_seed on grass via farming tool; two-stage
  growth (sprout → sapling → young tree, ~1 min/stage); matures into
  a harvestable FOREST resource tile
- Tile recovery: Nisse chops start a 5-min DARK_GRASS→GRASS timer;
  terrain canvas updated live via WorldSystem.refreshTerrainTile()
- New TreeSeedlingSystem manages sprites, growth ticking, maturation
- BootScene generates seedling_0/1/2 textures procedurally
- FarmingSystem adds tree_seed to tool cycle (F key)
- Stockpile panel shows tree_seed (default: 5); panel height adjusted
- StateManager v5: treeSeedlings + tileRecovery in WorldState
- WorldSystem uses CanvasTexture for live single-pixel updates

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CHANGELOG.md

@@ -7,6 +7,15 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## [Unreleased]
 
+### Added
+- **Unified Tile System** (Issue #14):
+  - Tree seedlings: player plants `tree_seed` on grass/dark-grass via the F-key farming tool; seedling grows through two stages (sprout → sapling → young tree, ~1 min each); on maturity it becomes a FOREST tile with a harvestable tree resource
+  - Tile recovery: when a Nisse chops a tree, the resulting DARK_GRASS tile starts a 5-minute recovery timer and reverts to GRASS automatically, with the terrain canvas updated in real time
+  - Three new procedural seedling textures (`seedling_0/1/2`) generated in BootScene
+  - `tree_seed` added to stockpile display (default 5 at game start) and to the farming tool cycle
+  - `WorldSystem.refreshTerrainTile()` updates the terrain canvas for a single tile without regenerating the full background
+  - New `TreeSeedlingSystem` manages seedling sprites, growth ticking, and maturation
+
 ### Added
 - **Nisse Info Panel** (Issue #9): clicking a Nisse opens a top-left panel with name, AI status, energy bar, active job, job priority buttons, and a live work log (last 10 of 20 runtime entries); closes with ESC, ✕ button, or by clicking another Nisse
 - Work log tracks: walking to job, hauling to stockpile, going to sleep, waking up, chopped/mined/farmed results, deposited at stockpile

src/StateManager.ts

@@ -1,5 +1,6 @@
-import { SAVE_KEY, WORLD_TILES, CROP_CONFIGS } from './config'
+import { SAVE_KEY, WORLD_TILES, CROP_CONFIGS, TREE_SEEDLING_STAGE_MS, TILE_RECOVERY_MS } from './config'
 import type { GameStateData, GameAction, PlayerState, WorldState, ItemId } from './types'
+import { TileType } from './types'
 
 const DEFAULT_PLAYER: PlayerState = {
   id: 'player1',
@@ -15,13 +16,15 @@ function makeEmptyWorld(seed: number): WorldState {
     buildings: {},
     crops: {},
     villagers: {},
-    stockpile: { wood: 10, stone: 5, wheat_seed: 10, carrot_seed: 5, wheat: 0, carrot: 0 },
+    stockpile: { wood: 10, stone: 5, wheat_seed: 10, carrot_seed: 5, wheat: 0, carrot: 0, tree_seed: 5 },
+    treeSeedlings: {},
+    tileRecovery: {},
   }
 }
 
 function makeDefaultState(): GameStateData {
   return {
-    version: 4,
+    version: 5,
     world: makeEmptyWorld(Math.floor(Math.random() * 999999)),
     player: { ...DEFAULT_PLAYER, inventory: { ...DEFAULT_PLAYER.inventory } },
   }
@@ -146,6 +149,26 @@ class StateManager {
         if (v) v.priorities = { ...action.priorities }
         break
       }
+
+      case 'PLANT_TREE_SEED': {
+        w.treeSeedlings[action.seedling.id] = { ...action.seedling }
+        w.stockpile.tree_seed = Math.max(0, (w.stockpile.tree_seed ?? 0) - 1)
+        // Cancel any tile recovery on this tile
+        delete w.tileRecovery[`${action.seedling.tileX},${action.seedling.tileY}`]
+        break
+      }
+
+      case 'REMOVE_TREE_SEEDLING':
+        delete w.treeSeedlings[action.seedlingId]
+        break
+
+      case 'SPAWN_RESOURCE':
+        w.resources[action.resource.id] = { ...action.resource }
+        break
+
+      case 'TILE_RECOVERY_START':
+        w.tileRecovery[`${action.tileX},${action.tileY}`] = TILE_RECOVERY_MS
+        break
     }
   }
 
@@ -163,6 +186,47 @@ class StateManager {
     return advanced
   }
 
+  /**
+   * Advances all tree-seedling growth timers.
+   * Returns IDs of seedlings that have reached stage 2 (ready to mature into a tree).
+   * @param delta - Frame delta in milliseconds
+   * @returns Array of seedling IDs that are now mature
+   */
+  tickSeedlings(delta: number): string[] {
+    const advanced: string[] = []
+    for (const s of Object.values(this.state.world.treeSeedlings)) {
+      s.stageTimerMs -= delta
+      if (s.stageTimerMs <= 0) {
+        s.stage = Math.min(s.stage + 1, 2)
+        s.stageTimerMs = TREE_SEEDLING_STAGE_MS
+        advanced.push(s.id)
+      }
+    }
+    return advanced
+  }
+
+  /**
+   * Ticks tile-recovery timers.
+   * Returns keys ("tileX,tileY") of tiles that have now recovered back to GRASS.
+   * @param delta - Frame delta in milliseconds
+   * @returns Array of recovered tile keys
+   */
+  tickTileRecovery(delta: number): string[] {
+    const recovered: string[] = []
+    const rec = this.state.world.tileRecovery
+    for (const key of Object.keys(rec)) {
+      rec[key] -= delta
+      if (rec[key] <= 0) {
+        delete rec[key]
+        recovered.push(key)
+        // Update tiles array directly (DARK_GRASS → GRASS)
+        const [tx, ty] = key.split(',').map(Number)
+        this.state.world.tiles[ty * WORLD_TILES + tx] = TileType.GRASS
+      }
+    }
+    return recovered
+  }
+
   save(): void {
     try { localStorage.setItem(SAVE_KEY, JSON.stringify(this.state)) } catch (_) {}
   }
@@ -172,10 +236,12 @@ class StateManager {
       const raw = localStorage.getItem(SAVE_KEY)
       if (!raw) return null
       const p = JSON.parse(raw) as GameStateData
-      if (p.version !== 4) return null
+      if (p.version !== 5) return null
       if (!p.world.crops)          p.world.crops          = {}
       if (!p.world.villagers)      p.world.villagers      = {}
       if (!p.world.stockpile)      p.world.stockpile      = {}
+      if (!p.world.treeSeedlings)  p.world.treeSeedlings  = {}
+      if (!p.world.tileRecovery)   p.world.tileRecovery   = {}
       // Reset in-flight AI states to idle on load so runtime timers start fresh
       for (const v of Object.values(p.world.villagers)) {
         if (v.aiState === 'walking' || v.aiState === 'working') v.aiState = 'idle'

src/config.ts

@@ -46,5 +46,11 @@ export const VILLAGER_NAMES = [
   'Orla','Pike','Quinn','Rook','Sera','Tull','Uma','Vex',
 ]
 
-export const SAVE_KEY = 'tg_save_v4'
+export const SAVE_KEY = 'tg_save_v5'
 export const AUTOSAVE_INTERVAL = 30_000
+
+/** Milliseconds for one tree-seedling stage to advance (two stages = full tree). */
+export const TREE_SEEDLING_STAGE_MS = 60_000   // 1 min per stage → 2 min total
+
+/** Milliseconds before a bare DARK_GRASS tile (after tree felling) reverts to GRASS. */
+export const TILE_RECOVERY_MS = 300_000        // 5 minutes

src/scenes/BootScene.ts

@@ -20,6 +20,7 @@ export class BootScene extends Phaser.Scene {
     this.buildResourceTextures()
     this.buildPlayerTexture()
     this.buildCropTextures()
+    this.buildSeedlingTextures()
     this.buildUITextures()
     this.buildVillagerAndBuildingTextures()
     this.generateWorldIfNeeded()
@@ -287,6 +288,40 @@ export class BootScene extends Phaser.Scene {
     g3.generateTexture('crop_carrot_3', W, H); g3.destroy()
   }
 
+  // ─── Tree seedling textures (3 growth stages) ────────────────────────────
+
+  /**
+   * Generates textures for the three tree-seedling growth stages:
+   *   seedling_0 – small sprout
+   *   seedling_1 – sapling with leaves
+   *   seedling_2 – young tree (about to mature into a FOREST tile)
+   */
+  private buildSeedlingTextures(): void {
+    // Stage 0: tiny sprout
+    const g0 = this.add.graphics()
+    g0.fillStyle(0x6D4C41); g0.fillRect(10, 20, 4, 10)
+    g0.fillStyle(0x66BB6A); g0.fillEllipse(12, 16, 12, 8)
+    g0.fillStyle(0x4CAF50); g0.fillEllipse(12, 13, 8, 6)
+    g0.generateTexture('seedling_0', 24, 32); g0.destroy()
+
+    // Stage 1: sapling
+    const g1 = this.add.graphics()
+    g1.fillStyle(0x6D4C41); g1.fillRect(9, 15, 5, 16)
+    g1.fillStyle(0x4CAF50); g1.fillCircle(12, 12, 8)
+    g1.fillStyle(0x66BB6A, 0.7); g1.fillCircle(7, 16, 5); g1.fillCircle(17, 16, 5)
+    g1.fillStyle(0x81C784); g1.fillCircle(12, 8, 5)
+    g1.generateTexture('seedling_1', 24, 32); g1.destroy()
+
+    // Stage 2: young tree (mature, ready to become a resource)
+    const g2 = this.add.graphics()
+    g2.fillStyle(0x000000, 0.15); g2.fillEllipse(12, 28, 16, 6)
+    g2.fillStyle(0x6D4C41); g2.fillRect(9, 14, 6, 14)
+    g2.fillStyle(0x2E7D32); g2.fillCircle(12, 9, 10)
+    g2.fillStyle(0x388E3C); g2.fillCircle(7, 13, 7); g2.fillCircle(17, 13, 7)
+    g2.fillStyle(0x43A047); g2.fillCircle(12, 6, 7)
+    g2.generateTexture('seedling_2', 24, 32); g2.destroy()
+  }
+
   // ─── UI panel texture ─────────────────────────────────────────────────────
 
   private buildUITextures(): void {

src/scenes/GameScene.ts

@@ -1,5 +1,6 @@
 import Phaser from 'phaser'
 import { AUTOSAVE_INTERVAL, TILE_SIZE } from '../config'
+import { TileType } from '../types'
 import type { BuildingType } from '../types'
 import { stateManager } from '../StateManager'
 import { LocalAdapter } from '../NetworkAdapter'
@@ -10,6 +11,7 @@ import { BuildingSystem } from '../systems/BuildingSystem'
 import { FarmingSystem } from '../systems/FarmingSystem'
 import { VillagerSystem } from '../systems/VillagerSystem'
 import { DebugSystem } from '../systems/DebugSystem'
+import { TreeSeedlingSystem } from '../systems/TreeSeedlingSystem'
 
 export class GameScene extends Phaser.Scene {
   private adapter!: LocalAdapter
@@ -20,6 +22,7 @@ export class GameScene extends Phaser.Scene {
   private farmingSystem!: FarmingSystem
   villagerSystem!: VillagerSystem
   debugSystem!: DebugSystem
+  private treeSeedlingSystem!: TreeSeedlingSystem
   private autosaveTimer = 0
   private menuOpen = false
 
@@ -39,6 +42,7 @@ export class GameScene extends Phaser.Scene {
     this.farmingSystem  = new FarmingSystem(this, this.adapter)
     this.villagerSystem      = new VillagerSystem(this, this.adapter, this.worldSystem)
     this.villagerSystem.init(this.resourceSystem, this.farmingSystem)
+    this.treeSeedlingSystem  = new TreeSeedlingSystem(this, this.adapter, this.worldSystem)
     this.debugSystem         = new DebugSystem(this, this.villagerSystem, this.worldSystem)
 
     this.worldSystem.create()
@@ -59,6 +63,10 @@ export class GameScene extends Phaser.Scene {
     this.farmingSystem.create()
     this.farmingSystem.onMessage     = (msg)         => this.events.emit('toast', msg)
     this.farmingSystem.onToolChange  = (tool, label) => this.events.emit('farmToolChanged', tool, label)
+    this.farmingSystem.onPlantTreeSeed = (tileX, tileY, tile) =>
+      this.treeSeedlingSystem.plantSeedling(tileX, tileY, tile)
+
+    this.treeSeedlingSystem.create()
 
     this.villagerSystem.create()
     this.villagerSystem.onMessage    = (msg) => this.events.emit('toast', msg)
@@ -70,6 +78,8 @@ export class GameScene extends Phaser.Scene {
     this.adapter.onAction = (action) => {
       if (action.type === 'CHANGE_TILE') {
         this.worldSystem.setTile(action.tileX, action.tileY, action.tile)
+      } else if (action.type === 'SPAWN_RESOURCE') {
+        this.resourceSystem.spawnResourcePublic(action.resource)
       }
     }
 
@@ -102,9 +112,17 @@ export class GameScene extends Phaser.Scene {
 
     this.resourceSystem.update(delta)
     this.farmingSystem.update(delta)
+    this.treeSeedlingSystem.update(delta)
     this.villagerSystem.update(delta)
     this.debugSystem.update()
 
+    // Tick tile-recovery timers; refresh canvas for any tiles that reverted to GRASS
+    const recovered = stateManager.tickTileRecovery(delta)
+    for (const key of recovered) {
+      const [tx, ty] = key.split(',').map(Number)
+      this.worldSystem.refreshTerrainTile(tx, ty, TileType.GRASS)
+    }
+
     this.events.emit('cameraMoved', this.cameraSystem.getCenterTile())
     this.buildingSystem.update()
 
@@ -144,6 +162,7 @@ export class GameScene extends Phaser.Scene {
     this.resourceSystem.destroy()
     this.buildingSystem.destroy()
     this.farmingSystem.destroy()
+    this.treeSeedlingSystem.destroy()
     this.villagerSystem.destroy()
   }
 }

src/scenes/UIScene.ts

@@ -6,7 +6,7 @@ import { stateManager } from '../StateManager'
 
 const ITEM_ICONS: Record<string, string> = {
   wood: '🪵', stone: '🪨', wheat_seed: '🌱', carrot_seed: '🥕',
-  wheat: '🌾', carrot: '🧡',
+  wheat: '🌾', carrot: '🧡', tree_seed: '🌲',
 }
 
 export class UIScene extends Phaser.Scene {
@@ -119,14 +119,14 @@ export class UIScene extends Phaser.Scene {
   /** Creates the stockpile panel in the top-right corner with item rows and population count. */
   private createStockpilePanel(): void {
     const x = this.scale.width - 178, y = 10
-    this.stockpilePanel = this.add.rectangle(x, y, 168, 165, 0x000000, 0.72).setOrigin(0, 0).setScrollFactor(0).setDepth(100)
+    this.stockpilePanel = this.add.rectangle(x, y, 168, 187, 0x000000, 0.72).setOrigin(0, 0).setScrollFactor(0).setDepth(100)
     this.stockpileTitleText = this.add.text(x + 10, y + 7, '⚡ STOCKPILE', { fontSize: '11px', color: '#aaaaaa', fontFamily: 'monospace' }).setScrollFactor(0).setDepth(101)
-    const items = ['wood','stone','wheat_seed','carrot_seed','wheat','carrot'] as const
+    const items = ['wood','stone','wheat_seed','carrot_seed','tree_seed','wheat','carrot'] as const
     items.forEach((item, i) => {
       const t = this.add.text(x + 10, y + 26 + i * 22, `${ITEM_ICONS[item]} ${item}: 0`, { fontSize: '13px', color: '#88dd88', fontFamily: 'monospace' }).setScrollFactor(0).setDepth(101)
       this.stockpileTexts.set(item, t)
     })
-    this.popText = this.add.text(x + 10, y + 145, '👥 Nisse: 0 / 0', { fontSize: '11px', color: '#aaaaaa', fontFamily: 'monospace' }).setScrollFactor(0).setDepth(101)
+    this.popText = this.add.text(x + 10, y + 167, '👥 Nisse: 0 / 0', { fontSize: '11px', color: '#aaaaaa', fontFamily: 'monospace' }).setScrollFactor(0).setDepth(101)
   }
 
   /** Refreshes all item quantities and colors in the stockpile panel. */

src/systems/FarmingSystem.ts

@@ -5,15 +5,16 @@ import type { CropKind, CropState, ItemId } from '../types'
 import { stateManager } from '../StateManager'
 import type { LocalAdapter } from '../NetworkAdapter'
 
-export type FarmingTool = 'none' | 'hoe' | 'wheat_seed' | 'carrot_seed' | 'water'
+export type FarmingTool = 'none' | 'hoe' | 'wheat_seed' | 'carrot_seed' | 'tree_seed' | 'water'
 
-const TOOL_CYCLE: FarmingTool[] = ['none', 'hoe', 'wheat_seed', 'carrot_seed', 'water']
+const TOOL_CYCLE: FarmingTool[] = ['none', 'hoe', 'wheat_seed', 'carrot_seed', 'tree_seed', 'water']
 
 const TOOL_LABELS: Record<FarmingTool, string> = {
   none:        '— None',
   hoe:         '⛏  Hoe  (till grass)',
   wheat_seed:  '🌾 Wheat Seeds',
   carrot_seed: '🥕 Carrot Seeds',
+  tree_seed:   '🌲 Tree Seeds (plant on grass)',
   water:       '💧 Watering Can',
 }
 
@@ -30,6 +31,14 @@ export class FarmingSystem {
   onToolChange?: (tool: FarmingTool, label: string) => void
   /** Emitted for toast notifications */
   onMessage?: (msg: string) => void
+  /**
+   * Called when the player uses the tree_seed tool on a tile.
+   * @param tileX - Target tile column
+   * @param tileY - Target tile row
+   * @param underlyingTile - The tile type at that position
+   * @returns true if planting succeeded, false if validation failed
+   */
+  onPlantTreeSeed?: (tileX: number, tileY: number, underlyingTile: TileType) => boolean
 
   constructor(scene: Phaser.Scene, adapter: LocalAdapter) {
     this.scene = scene
@@ -89,9 +98,27 @@ export class FarmingSystem {
 
     if (this.currentTool === 'hoe')            this.tillSoil(tileX, tileY, tile)
     else if (this.currentTool === 'water')     this.waterTile(tileX, tileY, tile)
+    else if (this.currentTool === 'tree_seed') this.plantTreeSeed(tileX, tileY, tile)
     else                                       this.plantCrop(tileX, tileY, tile, this.currentTool.replace('_seed', '') as CropKind)
   }
 
+  /**
+   * Delegates tree-seedling planting to the registered callback (TreeSeedlingSystem).
+   * Only works on GRASS or DARK_GRASS tiles. Shows a toast on success or failure.
+   * @param tileX - Target tile column
+   * @param tileY - Target tile row
+   * @param tile  - Current tile type at that position
+   */
+  private plantTreeSeed(tileX: number, tileY: number, tile: TileType): void {
+    if (tile !== TileType.GRASS && tile !== TileType.DARK_GRASS) {
+      this.onMessage?.('Plant tree seeds on grass!')
+      return
+    }
+    const ok = this.onPlantTreeSeed?.(tileX, tileY, tile)
+    if (ok === false) this.onMessage?.('No tree seeds, or tile is occupied!')
+    else if (ok)      this.onMessage?.('Tree seed planted! 🌱 (~2 min to grow)')
+  }
+
   private tillSoil(tileX: number, tileY: number, tile: TileType): void {
     if (tile !== TileType.GRASS && tile !== TileType.DARK_GRASS) {
       this.onMessage?.('Hoe only works on grass!')

src/systems/ResourceSystem.ts

@@ -76,6 +76,16 @@ export class ResourceSystem {
     this.removeSprite(id)
   }
 
+  /**
+   * Spawns a sprite for a resource that was created at runtime
+   * (e.g. a tree grown from a seedling). The resource must already be
+   * present in the game state when this is called.
+   * @param node - The resource node to render
+   */
+  public spawnResourcePublic(node: ResourceNodeState): void {
+    this.spawnSprite(node)
+  }
+
   /** Called when WorldSystem changes a tile (e.g. after tree removed) */
   syncTileChange(tileX: number, tileY: number, worldSystem: { setTile: (x: number, y: number, type: TileType) => void }): void {
     const state = stateManager.getState()

src/systems/TreeSeedlingSystem.ts

@@ -0,0 +1,131 @@
+import Phaser from 'phaser'
+import { TILE_SIZE, TREE_SEEDLING_STAGE_MS } from '../config'
+import { TileType, PLANTABLE_TILES } from '../types'
+import type { TreeSeedlingState } from '../types'
+import { stateManager } from '../StateManager'
+import type { LocalAdapter } from '../NetworkAdapter'
+import type { WorldSystem } from './WorldSystem'
+
+export class TreeSeedlingSystem {
+  private scene: Phaser.Scene
+  private adapter: LocalAdapter
+  private worldSystem: WorldSystem
+  private sprites = new Map<string, Phaser.GameObjects.Image>()
+
+  /**
+   * @param scene       - The Phaser scene this system belongs to
+   * @param adapter     - Network adapter for dispatching state actions
+   * @param worldSystem - Used to refresh the terrain canvas when a seedling matures
+   */
+  constructor(scene: Phaser.Scene, adapter: LocalAdapter, worldSystem: WorldSystem) {
+    this.scene = scene
+    this.adapter = adapter
+    this.worldSystem = worldSystem
+  }
+
+  /** Spawns sprites for all seedlings that exist in the saved state. */
+  create(): void {
+    const state = stateManager.getState()
+    for (const s of Object.values(state.world.treeSeedlings)) {
+      this.spawnSprite(s)
+    }
+  }
+
+  /**
+   * Ticks all seedling growth timers and handles stage changes.
+   * Stage 0→1: updates the sprite to the sapling texture.
+   * Stage 1→2: removes the seedling, spawns a tree resource, and updates the terrain canvas.
+   * @param delta - Frame delta in milliseconds
+   */
+  update(delta: number): void {
+    const advanced = stateManager.tickSeedlings(delta)
+    for (const id of advanced) {
+      const state = stateManager.getState()
+      const seedling = state.world.treeSeedlings[id]
+      if (!seedling) continue
+
+      if (seedling.stage === 2) {
+        // Fully mature: become a FOREST tile and a real tree resource
+        const { tileX, tileY } = seedling
+        this.removeSprite(id)
+        this.adapter.send({ type: 'REMOVE_TREE_SEEDLING', seedlingId: id })
+        this.adapter.send({ type: 'CHANGE_TILE', tileX, tileY, tile: TileType.FOREST })
+        this.worldSystem.refreshTerrainTile(tileX, tileY, TileType.FOREST)
+
+        const resourceId = `tree_grown_${tileX}_${tileY}_${Date.now()}`
+        this.adapter.send({
+          type: 'SPAWN_RESOURCE',
+          resource: { id: resourceId, tileX, tileY, kind: 'tree', hp: 3 },
+        })
+      } else {
+        // Stage 0→1: update sprite to sapling
+        const sprite = this.sprites.get(id)
+        if (sprite) sprite.setTexture(`seedling_${seedling.stage}`)
+      }
+    }
+  }
+
+  /**
+   * Attempts to plant a tree seedling on a grass tile.
+   * Validates that the stockpile has at least one tree_seed, the tile type is
+   * plantable (GRASS or DARK_GRASS), and no other object occupies the tile.
+   * @param tileX          - Target tile column
+   * @param tileY          - Target tile row
+   * @param underlyingTile - The current tile type (stored on the seedling for later restoration)
+   * @returns true if the seedling was planted, false if validation failed
+   */
+  plantSeedling(tileX: number, tileY: number, underlyingTile: TileType): boolean {
+    const state = stateManager.getState()
+
+    if ((state.world.stockpile.tree_seed ?? 0) <= 0) return false
+    if (!PLANTABLE_TILES.has(underlyingTile)) return false
+
+    const occupied =
+      Object.values(state.world.resources).some(r => r.tileX === tileX && r.tileY === tileY) ||
+      Object.values(state.world.buildings).some(b => b.tileX === tileX && b.tileY === tileY) ||
+      Object.values(state.world.crops).some(c => c.tileX === tileX && c.tileY === tileY) ||
+      Object.values(state.world.treeSeedlings).some(s => s.tileX === tileX && s.tileY === tileY)
+
+    if (occupied) return false
+
+    const id = `seedling_${tileX}_${tileY}_${Date.now()}`
+    const seedling: TreeSeedlingState = {
+      id, tileX, tileY,
+      stage: 0,
+      stageTimerMs: TREE_SEEDLING_STAGE_MS,
+      underlyingTile,
+    }
+
+    this.adapter.send({ type: 'PLANT_TREE_SEED', seedling })
+    this.spawnSprite(seedling)
+    return true
+  }
+
+  /**
+   * Creates and registers the sprite for a seedling.
+   * @param s - Seedling state to render
+   */
+  private spawnSprite(s: TreeSeedlingState): void {
+    const x = (s.tileX + 0.5) * TILE_SIZE
+    const y = (s.tileY + 0.5) * TILE_SIZE
+    const key = `seedling_${Math.min(s.stage, 2)}`
+    const sprite = this.scene.add.image(x, y, key)
+      .setOrigin(0.5, 0.85)
+      .setDepth(5)
+    this.sprites.set(s.id, sprite)
+  }
+
+  /**
+   * Destroys the sprite for a seedling and removes it from the registry.
+   * @param id - Seedling ID
+   */
+  private removeSprite(id: string): void {
+    const s = this.sprites.get(id)
+    if (s) { s.destroy(); this.sprites.delete(id) }
+  }
+
+  /** Destroys all seedling sprites and clears the registry. */
+  destroy(): void {
+    for (const id of [...this.sprites.keys()]) this.removeSprite(id)
+  }
+}

src/systems/VillagerSystem.ts

@@ -276,6 +276,8 @@ export class VillagerSystem {
         this.adapter.send({ type: 'VILLAGER_HARVEST_RESOURCE', villagerId: v.id, resourceId: job.targetId })
         // Clear the FOREST tile so the area becomes passable for future pathfinding
         this.adapter.send({ type: 'CHANGE_TILE', tileX: res.tileX, tileY: res.tileY, tile: TileType.DARK_GRASS })
+        // Start recovery timer so DARK_GRASS reverts to GRASS after 5 minutes
+        this.adapter.send({ type: 'TILE_RECOVERY_START', tileX: res.tileX, tileY: res.tileY })
         this.resourceSystem.removeResource(job.targetId)
         this.addLog(v.id, '✓ Chopped tree (+2 wood)')
       }

src/systems/WorldSystem.ts

@@ -21,6 +21,7 @@ export class WorldSystem {
   private tileset!: Phaser.Tilemaps.Tileset
   private bgImage!: Phaser.GameObjects.Image
   private builtLayer!: Phaser.Tilemaps.TilemapLayer
+  private bgCanvasTexture!: Phaser.Textures.CanvasTexture
 
   /** @param scene - The Phaser scene this system belongs to */
   constructor(scene: Phaser.Scene) {
@@ -35,10 +36,8 @@ export class WorldSystem {
     const state = stateManager.getState()
 
     // --- Canvas background (1px per tile, scaled up, LINEAR filtered) ---
-    const canvas = document.createElement('canvas')
-    canvas.width = WORLD_TILES
-    canvas.height = WORLD_TILES
-    const ctx = canvas.getContext('2d')!
+    const canvasTexture = this.scene.textures.createCanvas('terrain_bg', WORLD_TILES, WORLD_TILES) as Phaser.Textures.CanvasTexture
+    const ctx = canvasTexture.context
 
     for (let y = 0; y < WORLD_TILES; y++) {
       for (let x = 0; x < WORLD_TILES; x++) {
@@ -48,12 +47,14 @@ export class WorldSystem {
       }
     }
 
-    this.scene.textures.addCanvas('terrain_bg', canvas)
+    canvasTexture.refresh()
+    this.bgCanvasTexture = canvasTexture
+
     this.bgImage = this.scene.add.image(0, 0, 'terrain_bg')
       .setOrigin(0, 0)
       .setScale(TILE_SIZE)
       .setDepth(0)
-    this.scene.textures.get('terrain_bg').setFilter(Phaser.Textures.FilterMode.LINEAR)
+    canvasTexture.setFilter(Phaser.Textures.FilterMode.LINEAR)
 
     // --- Built tile layer (sparse — only FLOOR, WALL, TILLED_SOIL, WATERED_SOIL) ---
     this.map = this.scene.make.tilemap({
@@ -157,6 +158,21 @@ export class WorldSystem {
     return state.world.tiles[tileY * WORLD_TILES + tileX] as TileType
   }
 
+  /**
+   * Updates a single tile's pixel on the background canvas and refreshes the GPU texture.
+   * Used when a natural tile changes at runtime (e.g. DARK_GRASS → GRASS after recovery,
+   * or GRASS → FOREST when a seedling matures).
+   * @param tileX - Tile column
+   * @param tileY - Tile row
+   * @param type  - New tile type to reflect visually
+   */
+  refreshTerrainTile(tileX: number, tileY: number, type: TileType): void {
+    const color = BIOME_COLORS[type] ?? '#0a2210'
+    this.bgCanvasTexture.context.fillStyle = color
+    this.bgCanvasTexture.context.fillRect(tileX, tileY, 1, 1)
+    this.bgCanvasTexture.refresh()
+  }
+
   /** Destroys the tilemap and background image. */
   destroy(): void {
     this.map.destroy()

src/types.ts

@@ -20,7 +20,10 @@ export const IMPASSABLE = new Set<number>([
   TileType.WALL,
 ])
 
-export type ItemId = 'wood' | 'stone' | 'wheat_seed' | 'carrot_seed' | 'wheat' | 'carrot'
+/** Tiles on which tree seedlings may be planted. */
+export const PLANTABLE_TILES = new Set<TileType>([TileType.GRASS, TileType.DARK_GRASS])
+
+export type ItemId = 'wood' | 'stone' | 'wheat_seed' | 'carrot_seed' | 'wheat' | 'carrot' | 'tree_seed'
 
 export type BuildingType = 'floor' | 'wall' | 'chest' | 'bed' | 'stockpile_zone'
 
@@ -90,6 +93,18 @@ export interface PlayerState {
   inventory: Partial<Record<ItemId, number>>
 }
 
+export interface TreeSeedlingState {
+  id: string
+  tileX: number
+  tileY: number
+  /** Growth stage: 0 = sprout, 1 = sapling, 2 = mature (converts to resource). */
+  stage: number
+  /** Time remaining until next stage advance, in milliseconds. */
+  stageTimerMs: number
+  /** The tile type that was under the seedling when planted (GRASS or DARK_GRASS). */
+  underlyingTile: TileType
+}
+
 export interface WorldState {
   seed: number
   tiles: number[]
@@ -98,6 +113,13 @@ export interface WorldState {
   crops: Record<string, CropState>
   villagers: Record<string, VillagerState>
   stockpile: Partial<Record<ItemId, number>>
+  /** Planted tree seedlings, keyed by ID. */
+  treeSeedlings: Record<string, TreeSeedlingState>
+  /**
+   * Recovery timers for DARK_GRASS tiles, keyed by "tileX,tileY".
+   * Value is remaining milliseconds until the tile reverts to GRASS.
+   */
+  tileRecovery: Record<string, number>
 }
 
 export interface GameStateData {
@@ -123,3 +145,7 @@ export type GameAction =
   | { type: 'VILLAGER_HARVEST_CROP';    villagerId: string; cropId: string }
   | { type: 'VILLAGER_DEPOSIT';         villagerId: string }
   | { type: 'UPDATE_PRIORITIES';        villagerId: string; priorities: JobPriorities }
+  | { type: 'PLANT_TREE_SEED';         seedling: TreeSeedlingState }
+  | { type: 'REMOVE_TREE_SEEDLING';    seedlingId: string }
+  | { type: 'SPAWN_RESOURCE';          resource: ResourceNodeState }
+  | { type: 'TILE_RECOVERY_START';     tileX: number; tileY: number }