One word...
Perfection. Smooth animation, great sound, with an occasional head being bitten off. Challenging enough to allow replay, but not impossible. After a couple hours of trying, I finally beat level one. I might actually consider getting the ps2 version of this, assuming there are more types of weapons/attacks/enemies. Too bad there is only one level here. I have never seen a flash game that plays as well as this. A lot of work obviously went into this game. Good job.