Added in a doorway that opens when you collect all the coins. The doorway also tells the camera to switch to the boss room instead of following the player when they walk in the room.
I had a lot of problems getting the spawner and coins to work right. I'm using my own maker tool, and the spawner destroys all other spawners when it's loaded so that there's only one. Unfortunately my maker loads the object into memory so that it can clone it. Normally this is useful for things like the tiles, enemies, coins, etc, but in this case the invisible one was deleting all other spawners when I went into play mode instead of edit mode.
Next I intend to make Astrea (the witch girl) shoot out little fireballs for a few tiles, and the boss to move around. After that it's pretty much polish and extras. So almost to the minimum acceptable game.