Beat easy or normal mode to unlock "you almost have to try" mode. Seriously, the last boss involves holding down the mouse button and moving in a circle.
Not bad, but the boss tanks have way too many hit points. They're easy to kill, but it takes like two minutes. Half of the hit points they have would still be too much.
You can't tell what's an enemy and what's not once the floor starts getting covered in that weird multicolored "blood." Also the invincibility period after a hit is way too short.
I think something's wrong with the kill percentage. I've been absolutely sure that I've killed everything on a level with bomb spams and still gotten a 90% rating, whereas I've seen a couple enemies escape before and gotten 95%.