Very well made game! I always appreciate a simple gameplay loop over complex one. I do have a few critiques, but ultimately nothing major.
There seemed to be a bug where after killing an enemy you could still take a hit, like if the enemy was briefly alive and was just not visible. I believe a health-bar would've been great for the UI, since there wasn't really any way to take how much the player has. Finally, the main menu controls to start were unresponsive at times which made it hard to play the game.