Pretty good.
I don't see why people think this is so hard. Probably 'cause the majority of NG users have no skill in anything. The difficulty was fine. But there was one level that kinda pissed me off. The Asteroids level, being that it's random generated on each attempt, is sometimes impossible. It took about 8 tries before I was able to beat it 'cause most times the asteroids would trap me and fail in a horizontal line with no gaps large enough to fit through. And there was something about that Space Invaders level... It just felt... awkward. I'm not sure why but it didn't feel as smooth as the other levels.
Also, don't put hyperlinked logos in between levels. It's seriously fucking annoying accidentally opening new windows to your website 'cause I died on a button mashing stage.