Addictive, especially when you get a good set going, though explosive projectiles might be a bit OP. Like others have said, it's hard to tell the knight from everyone else, and he's pretty inconsequential compared to the actual enemies. You should consider changing the color palette for the enemies and arena, or just the knight. Also maybe a "you win" scene other than tallying up the total points would've been a nice touch, but more a taste thing then a major nitpick.