I really like the difficulty and gameplay of this loop :D i like the fast paced nature. enemies that die fast but spawn fast!
I think 1hp is good, no probs for me, the aiming is good - you adjust to not having 360 degrees angle..
Only suggestion I would give is to make the hitbox of the player smaller to be more generous - so it would feel more like "WUUH i got lucky", rather than "DANG did that hit me???"
really good job!