As a ghost, you can slingshot yourself around angry birds style with the mouse. As a zombie, wasd to move and click to shoot.
This is more like a weird sort of tech demo prototype, the kind of thing I could put on a resume to say "I made this in 48 hours and it works and functions almost correctly" more than a real game. If anyone wants to take this further, I will not stop you (but it would be nice to know about it so I can see where you take it). If you want the project files, shoot me a message pretty much anywhere with this username (reddit is good, twitter maybe, here or Ludum Dare, an email, whatever).
Oh yeah also I believe it crashes after the last level. That just means you finished!