I have been working on this on and off (as j can no doubt attest, more off than on), for a very long time now. It's slowly coming together, but I need it tested. Specifically, the SwitchTiles function. Just move the trap door tile around, and hit Debug to make sure it's reporting that it's in the right place. Also, in light of the last time I asked anyone to test it, let me know if absolutely nothing appears on the screen.