Cool concept here. I agree with others that the idea of losing screen space as you take damage was a great idea, but it was a bit too forgiving with the positioning, which made it almost a non-issue. Some repositioning of the cracks would make this a lot more effective.
There were a decent number of object interactions (spinning blades, arrow traps, and springy things), though you could have used the arrow and springs a bit more. The rooms were a little too easy I think. Especially the last room, where you can just go around the maze of spinning blades.
Not bad at all for a first game. Keep it up :)