Could definitely be improved by not having the buttons cover the playing area, especially on levels like D-5.
Also, why are there level slots that don't have a level in them?
This isn't just a bad game, it's a poorly constructed one.
Ignoring graphics, audio, and story problems: everything results in instant failure, the loading screen is derped, and the settings screen has nothing on it.
In which browser are you playing the game?