Not very innovative, but cool anyway. I'm also cool with the ammo limitation since you get an upgrade point if you're defeated anyways. That, however, makes the game run... unchallenging very fast. Adding to the unchallenging part, there is also the case of shuriken and arrows - very unbalanced when compared to the boulders late in the game.
The game is, all considered, fun to play, though. :D
the game is quite nice. the one problem for me was aiming- can't understand how it works... sometimes it is ok to aim straight to the head to get a hit, but other times you have to aim several pixels before it...
NEVER let your players run out of ammo! ALWAYS give some base weapon with unlimited ammo!