Fun idea for a game! Easy to pick up and enjoy.
Although, at the first play I didn't quite understand what to do after killing 5 of these birds, there's no visual hint or anything to let the player know they should move to the next arena.
The projectile is pretty much useless when I could just hold left click to hold a sword and instakill whatever came in contant with it.
Besides that, I like how easy the movement is and the unique buttons text (Charge and Retreat). Good job, keep it up :)