Realy nice mechanic. I needed to change my thinking when I have to release the Asteroids at first I always released them when they are between me and the enemy so that they vanished in a 90° to them. xD
Would be nice to see some Powerup like shield or higher pickup range.
Also since I like to play games on Itch not in Fullscreen it would be good if you can give the game frame a few pixels more, because of the Unity frame your game it is cutted at the top and the bottom so that I can' t see the score while playing.