I like the concept. My problems are:
enemies can spawn right on top of you
if you accidentely catch the ball, you can't shoot the enemies if they get too close
if the player movement speed was a bit faster, it would be easier to get to the ball and evade enemies.
But the concept is really clever, if you could get it working so the player never feels cheated and feels skillful instead of lucky, I think this could be a really fun game.
Nice job!