I'm not sure what was the goal of the game, since enemies were coming in a never ending stream and shooting them only pushed them slight away if they were not stuck in other enemies. I'm guessing I was supposed to push them off the arena ? If so, that's an interesting idea, but you might want to introduce the player more slowly to the objective: a simple level with a single enemy to push off the arena, so the player understands that's what they were supposed to do. Cause I ended up giving up seeing that the enemy spawn wouldn't stop and I didn't have any confirmation that I was doing the right thing.
Interesting concept.