I finally got around to playing this with my sister. Good stuff! It seems both players cannot hit the attack button at the same time. When that happens, it tends to favour one player over another. I'm not sure if this was intentional to prevent draws. But it does feel a little unfair.
Haha, I like the gruesome death animation when all lives are lost. All it needs now is a victory screen or something to show that the player won.
Also, I noticed that when you click to start, the controls show for a brief moment but then they quickly disappear from the game. If possible, maybe add the controls to the game page or make it so that the player has to press another key when the controls screen shows.
But that's pretty much all I can think of. Like I said in the thread, I promised to play it with someone, and I did. And it was a good experience. :