This is a really interesting game. I love the graphics and the music. (Though the music doesn't loop in boss fights so after a time it's just silence and sound effects.)
I wish there were a difficulty setting. I'm really bad at this and the time limit on these bosses just make it impossible. I manage to kill the red boss but after that I can't get anyone else. (even then I killed him at the 0 second mark, lucky.) Also, when I went to another boss, the red key was just chilling in the middle of the battle map.
It seems really fun. I'll have to keep playing to try and get better and see the ending at some point. (Right now it's been about half an hour and I need a break.)