diff --git a/src/game/combat.ts b/src/game/combat.ts
index eada4ac..f246ec8 100644
--- a/src/game/combat.ts
+++ b/src/game/combat.ts
@@ -22,6 +22,22 @@
  */
 import { numberCell, textCell } from './tables.ts'
 import type { DataTable } from './tables.ts'
+import {
+  allocatePacksToRooms,
+  partitionMapIntoRooms,
+  spawnMonsterPacksByRooms,
+  spawnPacksInRoom,
+} from './monster-rooms.ts'
+import type { MapRoom } from './monster-rooms.ts'
+
+export {
+  allocatePacksToRooms,
+  partitionMapIntoRooms,
+  spawnMonsterPacksByRooms,
+  spawnPacksInRoom,
+  type MapRoom,
+}
+
 
 /** Movement request and intent for one tick. */
 export interface CombatInput {
@@ -481,7 +497,11 @@ export function spawnMonsterPacks(
   spread: number,
   terrain: CombatTerrain,
   safeZones?: readonly SafeZone[],
+  rooms?: readonly MapRoom[],
 ): number {
+  if (rooms !== undefined && rooms.length > 0) {
+    return spawnMonsterPacksByRooms(world, packs, rooms, terrain, safeZones !== undefined ? { safeZones } : undefined)
+  }
   if (packs.length === 0) return 0
   let placed = 0
   let campIndex = 0
diff --git a/src/game/monster-rooms.ts b/src/game/monster-rooms.ts
new file mode 100644
index 0000000..1a31a21
--- /dev/null
+++ b/src/game/monster-rooms.ts
@@ -0,0 +1,544 @@
+/**
+ * Room-Local Monster Clustering and Placement.
+ *
+ * Replaces global spiral monster placement with authentic Diablo II room-based
+ * spatial clustering and allocation. In Diablo II, monsters are partitioned into
+ * rooms (sectors of ~20-30 cells outdoors, or discrete maze preset pieces indoors),
+ * avoiding player safe zones (towns, waypoint clearings, level entrances), with
+ * landmark SuperUniques fixed to their specific room and minions clustered tightly
+ * in camp rings around their leader.
+ */
+import type { CombatTerrain, CombatWorld, MonsterPack, SafeZone } from './combat.ts'
+import { Rng } from './rng.ts'
+
+/**
+ * A discrete spatial room or sector in a level.
+ */
+export interface MapRoom {
+  readonly id: string | number
+  readonly x: number       // world/scene pixels
+  readonly y: number
+  readonly width: number
+  readonly height: number
+  readonly cellX: number   // grid cell coordinates
+  readonly cellY: number
+  readonly cellsX: number
+  readonly cellsY: number
+  readonly isSafeZone?: boolean | undefined
+  readonly isPreset?: boolean | undefined
+}
+
+/**
+ * Options for partitioning a level map into rooms.
+ */
+export interface PartitionOptions {
+  /** Room cell size for outdoor grid sector partitioning (default ~24 cells). */
+  readonly roomCellSize?: number | undefined
+  /** Discrete maze rooms from the dungeon generator (e.g. from maze.ts). */
+  readonly mazeRooms?: readonly {
+    readonly x: number
+    readonly y: number
+    readonly width: number
+    readonly height: number
+    readonly id?: string | number | undefined
+    readonly isPreset?: boolean | undefined
+    readonly isSafeZone?: boolean | undefined
+  }[] | undefined
+  /** Circular exclusion zones where ordinary monster camps must not spawn. */
+  readonly safeZones?: readonly {
+    readonly x: number
+    readonly y: number
+    readonly radius: number
+  }[] | undefined
+  /** Cell pixel width (default 80 px). */
+  readonly cellPixelWidth?: number | undefined
+  /** Cell pixel height (default 80 px). */
+  readonly cellPixelHeight?: number | undefined
+  /** Uniform cell pixel size shorthand (default 80 px). */
+  readonly cellPixelSize?: number | undefined
+  /** Origin X offset in pixels (default 0). */
+  readonly originX?: number | undefined
+  /** Origin Y offset in pixels (default 0). */
+  readonly originY?: number | undefined
+}
+
+/** Default camp radius for room-local monster clustering (48~64 pixels). */
+export const PACK_RADIUS_PX = 64
+
+/**
+ * Check if a room boundary overlaps any safe zone circle.
+ * Tests in both pixel space and cell space for maximum compatibility.
+ */
+function checkSafeZoneOverlap(
+  x: number,
+  y: number,
+  width: number,
+  height: number,
+  cellX: number,
+  cellY: number,
+  cellsX: number,
+  cellsY: number,
+  safeZones?: readonly { readonly x: number; readonly y: number; readonly radius: number }[],
+): boolean {
+  if (safeZones === undefined || safeZones.length === 0) return false
+  for (const sz of safeZones) {
+    // Check in world pixel space
+    const clampPxX = Math.max(x, Math.min(sz.x, x + width))
+    const clampPxY = Math.max(y, Math.min(sz.y, y + height))
+    const pxDistSq = (sz.x - clampPxX) ** 2 + (sz.y - clampPxY) ** 2
+    if (pxDistSq <= sz.radius * sz.radius) return true
+
+    // Check in cell space (in case safeZone coordinates were given in cells)
+    const clampCellX = Math.max(cellX, Math.min(sz.x, cellX + cellsX))
+    const clampCellY = Math.max(cellY, Math.min(sz.y, cellY + cellsY))
+    const cellDistSq = (sz.x - clampCellX) ** 2 + (sz.y - clampCellY) ** 2
+    if (cellDistSq <= sz.radius * sz.radius) return true
+  }
+  return false
+}
+
+/**
+ * Partition a map into rooms.
+ *
+ * If `mazeRooms` are supplied (from dungeon generator), map them directly into `MapRoom`s.
+ * Otherwise (wilderness / outdoors), partition the level into authentic ~20-30 cell rooms
+ * (e.g. 24x24 cells = 120x120 subtiles), matching D2's room grid.
+ * Automatically flag rooms overlapping `safeZones` as `isSafeZone = true`.
+ *
+ * @param cellsX - total level width in cells.
+ * @param cellsY - total level height in cells.
+ * @param options - partitioning options.
+ * @returns partitioned MapRooms.
+ */
+export function partitionMapIntoRooms(
+  cellsX: number,
+  cellsY: number,
+  options?: PartitionOptions,
+): MapRoom[] {
+  const cellWidth = options?.cellPixelWidth ?? options?.cellPixelSize ?? 80
+  const cellHeight = options?.cellPixelHeight ?? options?.cellPixelSize ?? 80
+  const originX = options?.originX ?? 0
+  const originY = options?.originY ?? 0
+
+  if (options?.mazeRooms !== undefined && options.mazeRooms.length > 0) {
+    return options.mazeRooms.map((mr, index) => {
+      const cellX = mr.x
+      const cellY = mr.y
+      const rCellsX = mr.width
+      const rCellsY = mr.height
+      const x = cellX * cellWidth + originX
+      const y = cellY * cellHeight + originY
+      const width = rCellsX * cellWidth
+      const height = rCellsY * cellHeight
+      const id = mr.id ?? index
+      const isPreset = mr.isPreset ?? true
+      const isSafeZone = mr.isSafeZone ?? checkSafeZoneOverlap(
+        x, y, width, height, cellX, cellY, rCellsX, rCellsY, options.safeZones,
+      )
+
+      return {
+        id,
+        x,
+        y,
+        width,
+        height,
+        cellX,
+        cellY,
+        cellsX: rCellsX,
+        cellsY: rCellsY,
+        isPreset,
+        ...(isSafeZone ? { isSafeZone: true } : {}),
+      }
+    })
+  }
+
+  // Wilderness / outdoors: grid partition into ~24x24 cell rooms
+  const roomCellSize = options?.roomCellSize ?? 24
+  const rooms: MapRoom[] = []
+  let index = 0
+
+  for (let cy = 0; cy < cellsY; cy += roomCellSize) {
+    const rCellsY = Math.min(roomCellSize, cellsY - cy)
+    for (let cx = 0; cx < cellsX; cx += roomCellSize) {
+      const rCellsX = Math.min(roomCellSize, cellsX - cx)
+      const x = cx * cellWidth + originX
+      const y = cy * cellHeight + originY
+      const width = rCellsX * cellWidth
+      const height = rCellsY * cellHeight
+      const isSafeZone = checkSafeZoneOverlap(
+        x, y, width, height, cx, cy, rCellsX, rCellsY, options?.safeZones,
+      )
+
+      rooms.push({
+        id: index++,
+        x,
+        y,
+        width,
+        height,
+        cellX: cx,
+        cellY: cy,
+        cellsX: rCellsX,
+        cellsY: rCellsY,
+        isPreset: false,
+        ...(isSafeZone ? { isSafeZone: true } : {}),
+      })
+    }
+  }
+
+  return rooms
+}
+
+/**
+ * Allocate monster packs to rooms according to Diablo II rules:
+ * - Distributes non-landmark packs across non-safe rooms (avoiding town, stair buffers).
+ * - Fixed landmark packs (SuperUniques with `landmarkTile` or `fixedPosition`) route directly
+ *   to the room covering their coordinates.
+ * - Avoids over-crowding by balancing pack counts across candidate rooms based on room area.
+ *
+ * @param packs - list of monster packs to distribute.
+ * @param rooms - candidate rooms.
+ * @param seed - optional random seed for deterministic distribution.
+ * @returns Map from each MapRoom to its allocated MonsterPack array.
+ */
+export function allocatePacksToRooms(
+  packs: readonly MonsterPack[],
+  rooms: readonly MapRoom[],
+  seed?: number,
+): Map<MapRoom, MonsterPack[]> {
+  const allocation = new Map<MapRoom, MonsterPack[]>()
+  for (const room of rooms) {
+    allocation.set(room, [])
+  }
+  if (rooms.length === 0 || packs.length === 0) {
+    return allocation
+  }
+
+  const landmarkPacks: MonsterPack[] = []
+  const normalPacks: MonsterPack[] = []
+
+  for (const pack of packs) {
+    if (pack.fixedPosition !== undefined || pack.landmarkTile !== undefined) {
+      landmarkPacks.push(pack)
+    } else {
+      normalPacks.push(pack)
+    }
+  }
+
+  // 1. Fixed landmark SuperUniques route directly to their covering room
+  for (const pack of landmarkPacks) {
+    let targetRoom: MapRoom | undefined
+
+    if (pack.fixedPosition !== undefined) {
+      const fx = pack.fixedPosition.x
+      const fy = pack.fixedPosition.y
+      targetRoom = rooms.find(r => fx >= r.x && fx <= r.x + r.width && fy >= r.y && fy <= r.y + r.height)
+      if (targetRoom === undefined) {
+        // Fallback: nearest room center
+        let minDist = Infinity
+        for (const r of rooms) {
+          const cx = r.x + r.width / 2
+          const cy = r.y + r.height / 2
+          const d = Math.hypot(fx - cx, fy - cy)
+          if (d < minDist) {
+            minDist = d
+            targetRoom = r
+          }
+        }
+      }
+    } else if (pack.landmarkTile !== undefined) {
+      const tx = pack.landmarkTile.tileX
+      const ty = pack.landmarkTile.tileY
+      targetRoom = rooms.find(r => tx >= r.cellX && tx < r.cellX + r.cellsX && ty >= r.cellY && ty < r.cellY + r.cellsY)
+      if (targetRoom === undefined) {
+        targetRoom = rooms.find(r => tx >= r.cellX && tx <= r.cellX + r.cellsX && ty >= r.cellY && ty <= r.cellY + r.cellsY)
+      }
+      if (targetRoom === undefined) {
+        // Fallback: nearest room by cell center
+        let minDist = Infinity
+        for (const r of rooms) {
+          const cx = r.cellX + r.cellsX / 2
+          const cy = r.cellY + r.cellsY / 2
+          const d = Math.hypot(tx - cx, ty - cy)
+          if (d < minDist) {
+            minDist = d
+            targetRoom = r
+          }
+        }
+      }
+    }
+
+    if (targetRoom !== undefined && allocation.has(targetRoom)) {
+      allocation.get(targetRoom)!.push(pack)
+    }
+  }
+
+  // 2. Normal packs: distribute to non-safe rooms, balancing by room area
+  let candidateRooms = rooms.filter(r => !r.isSafeZone)
+  if (candidateRooms.length === 0) {
+    // Fallback if all rooms are marked safe
+    candidateRooms = rooms.slice()
+  }
+
+  const rng = new Rng(seed ?? 0x5eed)
+
+  for (const pack of normalPacks) {
+    // Score based on pack density: (currentCount + 1) / area
+    let minScore = Infinity
+    for (const r of candidateRooms) {
+      const count = allocation.get(r)!.length
+      const area = Math.max(1, r.cellsX * r.cellsY)
+      const score = (count + 1) / area
+      if (score < minScore) {
+        minScore = score
+      }
+    }
+
+    const bestRooms: MapRoom[] = []
+    for (const r of candidateRooms) {
+      const count = allocation.get(r)!.length
+      const area = Math.max(1, r.cellsX * r.cellsY)
+      const score = (count + 1) / area
+      if (Math.abs(score - minScore) < 1e-9) {
+        bestRooms.push(r)
+      }
+    }
+
+    const picked = bestRooms[rng.int(0, bestRooms.length - 1)]!
+    allocation.get(picked)!.push(pack)
+  }
+
+  return allocation
+}
+
+/**
+ * Spawns a single monster pack inside a given room.
+ */
+function spawnSinglePackInRoom(
+  world: CombatWorld,
+  pack: MonsterPack,
+  room: MapRoom,
+  terrain: CombatTerrain,
+): number {
+  if (pack.members.length === 0) return 0
+
+  const margin = Math.min(16, Math.max(2, room.width * 0.05), Math.max(2, room.height * 0.05))
+  const minSpawnX = room.x + margin
+  const maxSpawnX = room.x + room.width - margin
+  const minSpawnY = room.y + margin
+  const maxSpawnY = room.y + room.height - margin
+
+  // 1. Leader placement near room center or fixed landmark position
+  const startX = pack.fixedPosition !== undefined
+    ? pack.fixedPosition.x
+    : room.x + room.width / 2
+  const startY = pack.fixedPosition !== undefined
+    ? pack.fixedPosition.y
+    : room.y + room.height / 2
+
+  let leaderX = Math.max(minSpawnX, Math.min(maxSpawnX, startX))
+  let leaderY = Math.max(minSpawnY, Math.min(maxSpawnY, startY))
+  let leaderFound = false
+
+  // Check initial point
+  if (terrain.overlap(leaderX, leaderY) === 0) {
+    leaderFound = true
+  } else {
+    // Spiral search outward
+    const maxRadius = Math.max(room.width, room.height) / 2
+    for (let step = 1; step <= 64; step += 1) {
+      const angle = step * 2.399963
+      const radius = Math.min(maxRadius, step * 8)
+      const sx = Math.max(minSpawnX, Math.min(maxSpawnX, startX + Math.cos(angle) * radius))
+      const sy = Math.max(minSpawnY, Math.min(maxSpawnY, startY + Math.sin(angle) * radius))
+      if (terrain.overlap(sx, sy) === 0) {
+        leaderX = sx
+        leaderY = sy
+        leaderFound = true
+        break
+      }
+    }
+  }
+
+  // Grid fallback if spiral failed
+  if (!leaderFound) {
+    const stepX = Math.max(8, (maxSpawnX - minSpawnX) / 16)
+    const stepY = Math.max(8, (maxSpawnY - minSpawnY) / 16)
+    for (let gy = minSpawnY; gy <= maxSpawnY; gy += stepY) {
+      for (let gx = minSpawnX; gx <= maxSpawnX; gx += stepX) {
+        if (terrain.overlap(gx, gy) === 0) {
+          leaderX = gx
+          leaderY = gy
+          leaderFound = true
+          break
+        }
+      }
+      if (leaderFound) break
+    }
+  }
+
+  if (!leaderFound) return 0
+
+  const leaderDef = pack.members[0]!
+  world.monsters.push({
+    index: world.monsters.length,
+    stats: leaderDef,
+    x: leaderX,
+    y: leaderY,
+    hp: leaderDef.hp,
+    cooldown: 0,
+    state: 'idle',
+    facing: 0,
+    hitFlash: 0,
+    corpseTicks: 0,
+  })
+  let placed = 1
+
+  // 2. Minions placed in tight camp ring (PACK_RADIUS_PX = 48~64) around leader
+  const minions = pack.members.slice(1)
+  let minionPlaced = 0
+  let attempt = 0
+  const maxAttempts = minions.length * 32
+  const baseAngle = typeof room.id === 'number' ? room.id * 1.5 : 0.8
+  const effectiveRadius = Math.min(PACK_RADIUS_PX, Math.max(16, Math.min(room.width, room.height) / 2 - margin))
+
+  while (minionPlaced < minions.length && attempt < maxAttempts) {
+    attempt += 1
+    const angle = baseAngle + attempt * 2.399963
+    const distFrac = Math.sqrt(attempt / (minions.length * 12))
+    const radius = Math.min(effectiveRadius, 16 + (effectiveRadius - 16) * distFrac)
+    let mx = leaderX + Math.cos(angle) * radius
+    let my = leaderY + Math.sin(angle) * radius
+
+    // Clamps within room bounding boxes
+    mx = Math.max(minSpawnX, Math.min(maxSpawnX, mx))
+    my = Math.max(minSpawnY, Math.min(maxSpawnY, my))
+
+    // Respects terrain collisions
+    if (terrain.overlap(mx, my) > 0) continue
+
+    const minionDef = minions[minionPlaced]!
+    world.monsters.push({
+      index: world.monsters.length,
+      stats: minionDef,
+      x: mx,
+      y: my,
+      hp: minionDef.hp,
+      cooldown: 0,
+      state: 'idle',
+      facing: 0,
+      hitFlash: 0,
+      corpseTicks: 0,
+    })
+    minionPlaced += 1
+    placed += 1
+  }
+
+  return placed
+}
+
+/**
+ * Spawns monster pack(s) inside the boundaries of the specified `room`.
+ *
+ * Leader is positioned at a clear open sub-tile near the room's interior center;
+ * minions are placed in a tight camp ring (PACK_RADIUS_PX = 48~64) around the leader.
+ * Respects terrain collisions (terrain.overlap(x, y) === 0) and clamps within room
+ * bounding boxes (x in [minX + margin, maxX - margin]).
+ *
+ * @param world - the world to populate.
+ * @param pack - the pack or packs to spawn.
+ * @param room - the room boundary to spawn within.
+ * @param terrain - collision predicate.
+ * @returns how many monsters were placed.
+ */
+export function spawnPacksInRoom(
+  world: CombatWorld,
+  pack: MonsterPack | readonly MonsterPack[],
+  room: MapRoom,
+  terrain: CombatTerrain,
+): number {
+  if (Array.isArray(pack)) {
+    let count = 0
+    for (const p of pack) {
+      count += spawnSinglePackInRoom(world, p, room, terrain)
+    }
+    return count
+  }
+  return spawnSinglePackInRoom(world, pack as MonsterPack, room, terrain)
+}
+
+/** Alias for `spawnPacksInRoom` with singular naming. */
+export const spawnPackInRoom = spawnPacksInRoom
+
+/**
+ * Options for `spawnMonsterPacksByRooms`.
+ */
+export interface SpawnMonsterPacksByRoomsOptions {
+  readonly seed?: number | undefined
+  readonly safeZones?: readonly SafeZone[] | undefined
+  readonly spread?: number | undefined
+}
+
+/**
+ * Modern, clean replacement for `spawnMonsterPacks`, allocating packs across rooms
+ * and clustering members tightly within their assigned room boundaries.
+ *
+ * Also maintains backwards compatibility if plain packs with a center point are passed.
+ *
+ * @param world - world to populate.
+ * @param packs - monster packs to spawn.
+ * @param roomsOrAround - room array or fallback center point.
+ * @param terrain - collision predicate.
+ * @param options - allocation options or safe zones.
+ * @returns total monsters placed.
+ */
+export function spawnMonsterPacksByRooms(
+  world: CombatWorld,
+  packs: readonly MonsterPack[],
+  roomsOrAround: readonly MapRoom[] | { readonly x: number; readonly y: number },
+  terrain: CombatTerrain,
+  options?: SpawnMonsterPacksByRoomsOptions | readonly SafeZone[],
+): number {
+  if (packs.length === 0) return 0
+
+  let safeZones: readonly SafeZone[] | undefined
+  let seed: number | undefined
+  let spread = 600
+
+  if (Array.isArray(options)) {
+    safeZones = options
+  } else if (options !== undefined) {
+    const opts = options as SpawnMonsterPacksByRoomsOptions
+    safeZones = opts.safeZones
+    seed = opts.seed
+    if (opts.spread !== undefined) {
+      spread = opts.spread
+    }
+  }
+
+  if (!Array.isArray(roomsOrAround)) {
+    const around = roomsOrAround as { readonly x: number; readonly y: number }
+    const syntheticRooms = partitionMapIntoRooms(64, 64, {
+      roomCellSize: 16,
+      cellPixelSize: 80,
+      originX: around.x - spread,
+      originY: around.y - spread,
+      safeZones,
+    })
+    return spawnMonsterPacksByRooms(world, packs, syntheticRooms, terrain, {
+      safeZones,
+      seed,
+    })
+  }
+
+  const rooms = roomsOrAround as readonly MapRoom[]
+  if (rooms.length === 0) return 0
+
+  const allocation = allocatePacksToRooms(packs, rooms, seed)
+  let totalPlaced = 0
+  for (const [room, roomPacks] of allocation) {
+    for (const pack of roomPacks) {
+      totalPlaced += spawnPacksInRoom(world, pack, room, terrain)
+    }
+  }
+  return totalPlaced
+}
diff --git a/tests/monster-rooms.test.ts b/tests/monster-rooms.test.ts
new file mode 100644
index 0000000..4eca57b
--- /dev/null
+++ b/tests/monster-rooms.test.ts
@@ -0,0 +1,404 @@
+import { describe, expect, it } from 'vitest'
+import {
+  allocatePacksToRooms,
+  partitionMapIntoRooms,
+  spawnMonsterPacksByRooms,
+  spawnPacksInRoom,
+  PACK_RADIUS_PX,
+  type MapRoom,
+} from '../src/game/monster-rooms.ts'
+import { createWorld } from '../src/game/combat.ts'
+import type { CombatTerrain, MonsterPack, MonsterStats } from '../src/game/combat.ts'
+
+/** Flat open ground everywhere. */
+const OPEN: CombatTerrain = { overlap: () => 0 }
+
+/**
+ * Creates a simple monster stat record.
+ */
+function stats(id: string, hp = 30): MonsterStats {
+  return {
+    id,
+    name: id,
+    hp,
+    damage: 5,
+    cooldownTicks: 25,
+    reach: 40,
+    aggroRadius: 200,
+    speed: 100,
+    xp: 10,
+  }
+}
+
+/**
+ * Creates a test monster pack.
+ */
+function pack(id: string, count: number, extra?: Partial<MonsterPack>): MonsterPack {
+  return {
+    members: Array.from({ length: count }, (_, i) => stats(id, 30 + i)),
+    ...extra,
+  }
+}
+
+describe('Room-Local Monster Clustering and Placement', () => {
+  describe('partitionMapIntoRooms', () => {
+    it('partitions outdoor grid sectors into authentic ~20-30 cell rooms', () => {
+      // 72x48 cells partitioned with roomCellSize = 24 -> 3 x 2 = 6 rooms
+      const rooms = partitionMapIntoRooms(72, 48, { roomCellSize: 24, cellPixelSize: 80 })
+      expect(rooms).toHaveLength(6)
+
+      // All rooms should be 24x24 cells and 1920x1920 pixels
+      for (const room of rooms) {
+        expect(room.cellsX).toBe(24)
+        expect(room.cellsY).toBe(24)
+        expect(room.width).toBe(1920)
+        expect(room.height).toBe(1920)
+        expect(room.isPreset).toBe(false)
+      }
+
+      // Check cell grid coordinates
+      expect(rooms[0]?.cellX).toBe(0)
+      expect(rooms[0]?.cellY).toBe(0)
+      expect(rooms[1]?.cellX).toBe(24)
+      expect(rooms[1]?.cellY).toBe(0)
+      expect(rooms[2]?.cellX).toBe(48)
+      expect(rooms[2]?.cellY).toBe(0)
+      expect(rooms[3]?.cellX).toBe(0)
+      expect(rooms[3]?.cellY).toBe(24)
+    })
+
+    it('handles map dimensions that do not divide evenly by roomCellSize', () => {
+      // 50x30 cells with roomCellSize = 24 -> 3 cols (24, 24, 2) x 2 rows (24, 6) = 6 rooms
+      const rooms = partitionMapIntoRooms(50, 30, { roomCellSize: 24, cellPixelSize: 80 })
+      expect(rooms).toHaveLength(6)
+
+      const col2Row0 = rooms.find(r => r.cellX === 48 && r.cellY === 0)
+      expect(col2Row0).toBeDefined()
+      expect(col2Row0?.cellsX).toBe(2)
+      expect(col2Row0?.cellsY).toBe(24)
+      expect(col2Row0?.width).toBe(160)
+
+      const col0Row1 = rooms.find(r => r.cellX === 0 && r.cellY === 24)
+      expect(col0Row1).toBeDefined()
+      expect(col0Row1?.cellsX).toBe(24)
+      expect(col0Row1?.cellsY).toBe(6)
+      expect(col0Row1?.height).toBe(480)
+    })
+
+    it('maps discrete maze rooms directly into MapRooms', () => {
+      const mazeRooms = [
+        { x: 0, y: 0, width: 24, height: 24 },
+        { x: 24, y: 0, width: 24, height: 24 },
+        { x: 24, y: 24, width: 12, height: 12 },
+      ]
+      const rooms = partitionMapIntoRooms(48, 48, { mazeRooms, cellPixelSize: 80 })
+      expect(rooms).toHaveLength(3)
+
+      expect(rooms[0]?.isPreset).toBe(true)
+      expect(rooms[0]?.cellX).toBe(0)
+      expect(rooms[0]?.cellY).toBe(0)
+      expect(rooms[0]?.width).toBe(1920)
+
+      expect(rooms[2]?.cellsX).toBe(12)
+      expect(rooms[2]?.cellsY).toBe(12)
+      expect(rooms[2]?.width).toBe(960)
+      expect(rooms[2]?.height).toBe(960)
+    })
+
+    it('automatically flags rooms overlapping safe zones as isSafeZone', () => {
+      const safeZones = [
+        { x: 500, y: 500, radius: 160 },
+      ]
+      const rooms = partitionMapIntoRooms(72, 48, { roomCellSize: 24, cellPixelSize: 80, safeZones })
+      expect(rooms).toHaveLength(6)
+
+      // Room 0 covers [0, 1920] x [0, 1920], overlaps (500, 500)
+      expect(rooms[0]?.isSafeZone).toBe(true)
+
+      // Distant rooms should not be safe zones
+      const distantRoom = rooms.find(r => r.cellX === 48 && r.cellY === 24)
+      expect(distantRoom?.isSafeZone).toBeUndefined()
+    })
+  })
+
+  describe('allocatePacksToRooms', () => {
+    it('distributes normal packs to non-safe rooms and avoids safe rooms', () => {
+      const rooms: MapRoom[] = [
+        { id: 0, x: 0, y: 0, width: 1000, height: 1000, cellX: 0, cellY: 0, cellsX: 10, cellsY: 10, isSafeZone: true },
+        { id: 1, x: 1000, y: 0, width: 1000, height: 1000, cellX: 10, cellY: 0, cellsX: 10, cellsY: 10 },
+        { id: 2, x: 2000, y: 0, width: 1000, height: 1000, cellX: 20, cellY: 0, cellsX: 10, cellsY: 10 },
+      ]
+      const packs = [
+        pack('fallen', 3),
+        pack('zombie', 4),
+        pack('skeleton', 3),
+        pack('quillrat', 2),
+      ]
+
+      const allocation = allocatePacksToRooms(packs, rooms, 12345)
+
+      // Safe room (id: 0) must receive NO normal packs
+      expect(allocation.get(rooms[0]!)).toHaveLength(0)
+
+      // Remaining packs must be distributed between room 1 and room 2
+      const room1Count = allocation.get(rooms[1]!)?.length ?? 0
+      const room2Count = allocation.get(rooms[2]!)?.length ?? 0
+      expect(room1Count + room2Count).toBe(4)
+      expect(room1Count).toBeGreaterThan(0)
+      expect(room2Count).toBeGreaterThan(0)
+    })
+
+    it('balances pack counts across candidate rooms based on room area', () => {
+      // Room Small: 10x10 cells (area 100)
+      // Room Large: 20x20 cells (area 400 - 4x larger)
+      const roomSmall: MapRoom = { id: 'small', x: 0, y: 0, width: 800, height: 800, cellX: 0, cellY: 0, cellsX: 10, cellsY: 10 }
+      const roomLarge: MapRoom = { id: 'large', x: 800, y: 0, width: 1600, height: 1600, cellX: 10, cellY: 0, cellsX: 20, cellsY: 20 }
+      const rooms = [roomSmall, roomLarge]
+
+      const packs = Array.from({ length: 10 }, (_, i) => pack(`mob_${String(i)}`, 3))
+      const allocation = allocatePacksToRooms(packs, rooms, 42)
+
+      const smallCount = allocation.get(roomSmall)?.length ?? 0
+      const largeCount = allocation.get(roomLarge)?.length ?? 0
+
+      expect(smallCount + largeCount).toBe(10)
+      // Large room has 4x area, so it should receive significantly more packs without overcrowding small room
+      expect(largeCount).toBeGreaterThan(smallCount * 2)
+    })
+
+    it('routes landmark SuperUnique packs with landmarkTile to covering room', () => {
+      const roomA: MapRoom = { id: 'A', x: 0, y: 0, width: 1920, height: 1920, cellX: 0, cellY: 0, cellsX: 24, cellsY: 24 }
+      const roomB: MapRoom = { id: 'B', x: 1920, y: 0, width: 1920, height: 1920, cellX: 24, cellY: 0, cellsX: 24, cellsY: 24 }
+      const rooms = [roomA, roomB]
+
+      // Bishibosh at landmark tile (tileX: 30, tileY: 10) falls inside room B (cellX in [24, 48))
+      const bishiboshPack = pack('bishibosh', 5, {
+        superUniqueId: 'Bishibosh',
+        landmarkTile: { tileX: 30, tileY: 10 },
+      })
+      const normalPack = pack('fallen', 3)
+
+      const allocation = allocatePacksToRooms([bishiboshPack, normalPack], rooms, 100)
+
+      const roomBPacks = allocation.get(roomB) ?? []
+      expect(roomBPacks).toContain(bishiboshPack)
+    })
+
+    it('routes landmark SuperUnique packs with fixedPosition to covering room', () => {
+      const roomA: MapRoom = { id: 'A', x: 0, y: 0, width: 1000, height: 1000, cellX: 0, cellY: 0, cellsX: 10, cellsY: 10 }
+      const roomB: MapRoom = { id: 'B', x: 1000, y: 0, width: 1000, height: 1000, cellX: 10, cellY: 0, cellsX: 10, cellsY: 10 }
+      const rooms = [roomA, roomB]
+
+      // Rakanishu fixed at world pixel coordinates (1500, 500) inside room B
+      const rakanishuPack = pack('rakanishu', 4, {
+        superUniqueId: 'Rakanishu',
+        fixedPosition: { x: 1500, y: 500 },
+      })
+
+      const allocation = allocatePacksToRooms([rakanishuPack], rooms)
+      expect(allocation.get(roomB)).toContain(rakanishuPack)
+      expect(allocation.get(roomA)).toHaveLength(0)
+    })
+
+    it('is deterministic with a given seed', () => {
+      const rooms: MapRoom[] = [
+        { id: 1, x: 0, y: 0, width: 800, height: 800, cellX: 0, cellY: 0, cellsX: 10, cellsY: 10 },
+        { id: 2, x: 800, y: 0, width: 800, height: 800, cellX: 10, cellY: 0, cellsX: 10, cellsY: 10 },
+        { id: 3, x: 1600, y: 0, width: 800, height: 800, cellX: 20, cellY: 0, cellsX: 10, cellsY: 10 },
+      ]
+      const packs = Array.from({ length: 9 }, (_, i) => pack(`mob_${String(i)}`, 2))
+
+      const run1 = allocatePacksToRooms(packs, rooms, 9999)
+      const run2 = allocatePacksToRooms(packs, rooms, 9999)
+
+      for (const room of rooms) {
+        const p1 = run1.get(room)!.map(p => p.members[0]?.id)
+        const p2 = run2.get(room)!.map(p => p.members[0]?.id)
+        expect(p1).toEqual(p2)
+      }
+    })
+  })
+
+  describe('spawnPacksInRoom', () => {
+    it('places monster pack strictly within room boundaries', () => {
+      const world = createWorld(0, 0)
+      const room: MapRoom = {
+        id: 'test_room',
+        x: 1000,
+        y: 1000,
+        width: 400,
+        height: 400,
+        cellX: 10,
+        cellY: 10,
+        cellsX: 5,
+        cellsY: 5,
+      }
+      const testPack = pack('fallen', 6)
+
+      const placed = spawnPacksInRoom(world, testPack, room, OPEN)
+      expect(placed).toBe(6)
+      expect(world.monsters).toHaveLength(6)
+
+      // Verify every monster is strictly inside room bounds
+      for (const monster of world.monsters) {
+        expect(monster.x).toBeGreaterThanOrEqual(room.x)
+        expect(monster.x).toBeLessThanOrEqual(room.x + room.width)
+        expect(monster.y).toBeGreaterThanOrEqual(room.y)
+        expect(monster.y).toBeLessThanOrEqual(room.y + room.height)
+      }
+    })
+
+    it('respects terrain collisions and does not spill through walls', () => {
+      const world = createWorld(0, 0)
+      const room: MapRoom = {
+        id: 'walled_room',
+        x: 500,
+        y: 500,
+        width: 400,
+        height: 400,
+        cellX: 5,
+        cellY: 5,
+        cellsX: 5,
+        cellsY: 5,
+      }
+      // Vertical solid wall slicing through x in [680, 750]
+      const walledTerrain: CombatTerrain = {
+        overlap: (x: number) => (x >= 680 && x <= 750 ? 1 : 0),
+      }
+      const testPack = pack('zombie', 8)
+
+      const placed = spawnPacksInRoom(world, testPack, room, walledTerrain)
+      expect(placed).toBeGreaterThan(0)
+
+      for (const monster of world.monsters) {
+        // Must never land on solid wall
+        expect(walledTerrain.overlap(monster.x, monster.y)).toBe(0)
+        expect(monster.x < 680 || monster.x > 750).toBe(true)
+        // Must stay inside room
+        expect(monster.x).toBeGreaterThanOrEqual(room.x)
+        expect(monster.x).toBeLessThanOrEqual(room.x + room.width)
+        expect(monster.y).toBeGreaterThanOrEqual(room.y)
+        expect(monster.y).toBeLessThanOrEqual(room.y + room.height)
+      }
+    })
+
+    it('clusters minions tightly around leader within PACK_RADIUS_PX', () => {
+      const world = createWorld(0, 0)
+      const room: MapRoom = {
+        id: 'cluster_room',
+        x: 2000,
+        y: 2000,
+        width: 800,
+        height: 800,
+        cellX: 20,
+        cellY: 20,
+        cellsX: 10,
+        cellsY: 10,
+      }
+      const testPack = pack('fallen', 7)
+
+      spawnPacksInRoom(world, testPack, room, OPEN)
+      expect(world.monsters).toHaveLength(7)
+
+      const leader = world.monsters[0]!
+      const minions = world.monsters.slice(1)
+
+      for (const minion of minions) {
+        const dist = Math.hypot(minion.x - leader.x, minion.y - leader.y)
+        expect(dist).toBeLessThanOrEqual(PACK_RADIUS_PX)
+      }
+    })
+
+    it('positions leader near interior center of room on clear ground', () => {
+      const world = createWorld(0, 0)
+      const room: MapRoom = {
+        id: 'center_test',
+        x: 1000,
+        y: 1000,
+        width: 400,
+        height: 400,
+        cellX: 10,
+        cellY: 10,
+        cellsX: 5,
+        cellsY: 5,
+      }
+      const testPack = pack('boss', 1)
+
+      spawnPacksInRoom(world, testPack, room, OPEN)
+      expect(world.monsters).toHaveLength(1)
+
+      const leader = world.monsters[0]!
+      const roomCenterX = room.x + room.width / 2 // 1200
+      const roomCenterY = room.y + room.height / 2 // 1200
+
+      // Leader should land right at or very close to center
+      expect(Math.abs(leader.x - roomCenterX)).toBeLessThan(16)
+      expect(Math.abs(leader.y - roomCenterY)).toBeLessThan(16)
+    })
+
+    it('places fixedPosition SuperUnique at or near designated landmark coordinates', () => {
+      const world = createWorld(0, 0)
+      const room: MapRoom = {
+        id: 'landmark_room',
+        x: 0,
+        y: 0,
+        width: 1000,
+        height: 1000,
+        cellX: 0,
+        cellY: 0,
+        cellsX: 10,
+        cellsY: 10,
+      }
+      const testPack = pack('treehead', 1, {
+        superUniqueId: 'Treehead WoodFist',
+        fixedPosition: { x: 350, y: 450 },
+      })
+
+      spawnPacksInRoom(world, testPack, room, OPEN)
+      expect(world.monsters).toHaveLength(1)
+
+      const leader = world.monsters[0]!
+      expect(leader.x).toBe(350)
+      expect(leader.y).toBe(450)
+    })
+  })
+
+  describe('spawnMonsterPacksByRooms', () => {
+    it('populates world with all packs distributed across partitioned rooms', () => {
+      const world = createWorld(0, 0)
+      const rooms = partitionMapIntoRooms(48, 48, { roomCellSize: 24, cellPixelSize: 80 })
+      const packs = [
+        pack('fallen', 4),
+        pack('zombie', 3),
+        pack('skeleton', 5),
+      ]
+
+      const placed = spawnMonsterPacksByRooms(world, packs, rooms, OPEN, { seed: 101 })
+      expect(placed).toBe(12)
+      expect(world.monsters).toHaveLength(12)
+
+      // Verify every monster lies within at least one room's bounding box
+      for (const m of world.monsters) {
+        const inAnyRoom = rooms.some(
+          r => m.x >= r.x && m.x <= r.x + r.width && m.y >= r.y && m.y <= r.y + r.height,
+        )
+        expect(inAnyRoom).toBe(true)
+      }
+    })
+
+    it('maintains backwards compatibility when fallback around coordinates are passed', () => {
+      const world = createWorld(0, 0)
+      const packs = [pack('fallen', 3)]
+
+      const placed = spawnMonsterPacksByRooms(
+        world,
+        packs,
+        { x: 500, y: 500 },
+        OPEN,
+        { spread: 300 },
+      )
+      expect(placed).toBe(3)
+      expect(world.monsters).toHaveLength(3)
+    })
+  })
+})