I was playing the Windows build, and there is one very nasty bug: the game is not fullscreen, and it does not capture the cursor. So the only way to play it is to change the screen resolution to 1280x800 (and still it will cut off the bottom part of the game a bit).
Player movement felt too slow for the first-person shooter, and the player can only move one way (e.g. you can't move forward and strafe at the same time). It does not combine well with the requirement to move back-and-forth across the levels multiple times to fill the goal.
Physical level geometry sometimes does not match the visuals, e.g. I could go out of bounds through some hollow walls.
I would love to have anoption to restart the game at the beginning of the level (sorry if there is such an option in the bottom of the "You died" screen, I couldn't see it due to the issue explained above), as at some point you can die simply after spawning right on the enemy you don't even see.
The art style is great, very Madoka-like, and the music choice is very good too!