Gameplay loop is well designed! the pixel art is also charming, i didn't find the enemy attacks that annoying but that problem can be Easily avoided by the classic sfx advice which is Randomizing the pitch of the sfx every time it is played WHEN it is expect to be played so much. Another really cool thing to always keep in mind is to use subtle effect based backgrounds where possible (in the main menu, on the arena ground..), not hard since you're using unity or even godot!