i think game wasn't that hard. the only part i had problem was the Yellow Time limit part; but the problem was from me, not the game.
another thing that a little bothered me was the cost of changing your weapon mode. i don't know it was intentional or not or i am missing something , but when you start a level you have very little energy and if you accidently change your weapon , you should start over. it was a little bothersome especially in the Blue boss fight.