diff --git a/src/scripts/world.gd b/src/scripts/world.gd
index 9cfee9f..bfcd368 100644
--- a/src/scripts/world.gd
+++ b/src/scripts/world.gd
@@ -1,19 +1,24 @@
 extends Node2D
 
+const ROOMS_PER_DIFFICULTY := 1
+
 const door = preload("res://scenes/door.tscn")
 
 const main_room = preload("res://scenes/rooms/room_main.tscn")
-const rooms = [
-	preload("res://scenes/rooms/room1.tscn"),
-	preload("res://scenes/rooms/room2.tscn"),
-	preload("res://scenes/rooms/room3.tscn"),
-	preload("res://scenes/rooms/room-illuminati.tscn"),
-	preload("res://scenes/rooms/room-wheel.tscn"),
-	preload("res://scenes/rooms/room_4.tscn"),
-	preload("res://scenes/rooms/room-tunnel.tscn"),
-]
+const room_type := preload("res://scripts/room.gd")
+const rooms := {
+	room_type.difficulty.EASY: [preload("res://scenes/rooms/room3.tscn")],
+	room_type.difficulty.MEDIUM: [preload("res://scenes/rooms/room2.tscn")],
+	room_type.difficulty.HARD: [
+		preload("res://scenes/rooms/room1.tscn"),
+		preload("res://scenes/rooms/room-illuminati.tscn"),
+		preload("res://scenes/rooms/room-wheel.tscn"),
+		preload("res://scenes/rooms/room_4.tscn"),
+		preload("res://scenes/rooms/room-tunnel.tscn"),
+	]
+}
 
-var room_idx: int = -1
+var room_scene: PackedScene
 var room: Node2D
 
 const Spell = SpellBook.Spells
@@ -30,19 +35,30 @@ const spell_order = [
 ]
 var next_spell_idx := 0
 
+var next_difficulty := room_type.difficulty.EASY
+var count_until_next_difficulty := ROOMS_PER_DIFFICULTY
+
+func _update_difficulty():
+	count_until_next_difficulty -= 1
+	if count_until_next_difficulty == 0 and next_difficulty != room_type.difficulty.HARD:
+		next_difficulty += 1
+		count_until_next_difficulty = ROOMS_PER_DIFFICULTY
+
 ## Spawn a new room.
 func new_room():
-	var available_rooms = rooms.duplicate()
+	var available_rooms = rooms[next_difficulty].duplicate()
 	# avoid picking the same room again
-	if room_idx >= 0:
-		available_rooms.remove_at(room_idx)
+	available_rooms.erase(room_scene)
+	assert(available_rooms.size() > 0)
+	_update_difficulty()
 	load_room(available_rooms.pick_random())
 
 func load_room(scene: PackedScene):
 	if room:
 		room.queue_free()
 		await room.tree_exited
-	room = scene.instantiate()
+	room_scene = scene
+	room = room_scene.instantiate()
 	add_child(room)
 	check_room_cleared()
 	$Player.position = room.find_child("PlayerMarker").position