I was just able to make it to the 4th floor after a few tries.
Very cool game. I thought your take on the theme was really good and the game was fun to play once I figured it out (I didn't realize the exit for one level was next to the start... that's on me I guess :).
Tiny critique/opinion: I wish I could see the ghost health somewhere (after shooting them once so it doesn't ruin the mechanic where some good objects appear as ghosts). Without that, it's impossible to know how tough a ghost is on later levels.