Difficulty avoiding shots or too many enemies to kill at once. The last battle I did, there were more enemies than I could kill and it forced me to run away a lot. I love your AI by the way. Especially how sometimes they'll go around the other way and surprise me. The first round isn't too hard, the 2nd gets a tad harder but the 3rd is just soooooo manyyyyy lol. I gave it a few tries and it's an amazing shooter! Your level designs are highly detailed but not obnoxious as well!