This game is fun, but there seem to be some small frustrating bugs! Like if you're holding down fire, and you move, you stop firing, until you let go of SPACE and press it again.
Definitely a good difficulty for a flash game. I don't like games that I can just rush through in 15 minutes. Level 24 and 27 were the hardest for me, there is so much micro managing that needs to go on to beat yellow...