It's good
You have a great thing going here. You really deliver when it comes to your promise of a hard game, but, contrary to what some others have said, this game does have glitched that add unnecessary difficulty to the game. Collision is spotty, and Frank has an annoying habit of shooting up to the top of the screen when smacked. His threat range annoyed me a bit, especially for the back punch, but it made sense, seeing as how he's smaller then the others. I've gotten to the middle of the third site, and I'm gonna stop there for now, only because it's late and my arm's gettin' tired. A great little time waster, and if you have a cool head, can be a great stress reliever, too (just takin' out a bunch of Skullheads in one blow is pretty satisfying). The graphics lend it a great cartoony feel that blends with gameplay nicely, and it might've just me, but I could've sworn that the baddies were in tune with the music. Every time the music picked up, they started swarming anew. Whatever the case, be proud of your work. This is a great achievement. Good luck on your next one.
-Xanatos