Fighting enemies with cellular automata!

Enemies have now been added to the cave. Your defense: causing them to run into "lifed" tiles. You can give a block life by colliding with it. If a block has life, it turns green. The enemies will follow you constantly.

I uploaded another demo. If you have a slow computer you probably won't be able to play it. It runs between 14 and 20 FPS on my Intel Core 2 Duo machine with 4 gigs of RAM. Time to optimize!

I suspect people will develop their own ways of causing the enemies to run into lifed tiles, so post your strategies! I want make enemies that appeal to all playing styles!