New walker prefab (mushroom_red sprite) patrols a platform, turns at walls and ledges, drains a heart on contact and dies when stomped, bouncing the player up. Three are placed in level2. The level 2 spawn point is set to cell (7,11) so the player starts standing on the floor instead of falling in from mid-air, and level 1's LevelClear now loads level2.tscn.
