First, I was gonna rate this game 3/5, for having bugs in Chrome. But then I played in another browser, and I kinda like the upgrade system and the different enemies. So I rated 4/5 :P
If I quickly press and release 'z', I can jump higher than if I just hold 'z'. Also, a few other weapons (automatic fire) and upgrades may be cool. And the enemies should also get stronger when you progress. Pretty well made game, but needs inprovements. 3/5.
Frustrated Badge ( hard ~ 30 points )
You acquired this badge on Aug. 01, 2011.
=D I skipped level 25 and 29 though. And level 40 is really frustrating.