The concept is awesome and look of the game is great! The sounds were also great.
Some thoughts:
- I found coordinating the character change (z) with the jumping (x) to be a little challenging. Maybe could include another binding for either? Although not all players will have this issue I'm sure.
- My play session was ended by a buggy room. I got stuck in some room and couldn't leave.
- A small detail, but if the 'fire' sound effect when shooting a projectile could be a one shot I think it would help. The sound gets cut off when shooting too quickly.
Overall, great job!