Hey, here to return the favor of rating my game ;)
You have a nice game here, but I'm not really happy with it. There are a few things that should be changed:
- The movement of the character is a little to slippery for my personal preference.
- As others have mentioned, you should be able to use spacebar all the time and I would consider binding shoot and retract to the same button, or left and right mouse button.
- The enemies are spawning a little to random. I would check if the character is too close to a spawn point and avoid spawning enemies there. In this case the player will not be surprise by an enemy and gets a foul.
- I played until a score of 1100 or so (first try) and there was no increase in difficulty and the game felt a little boring after a while. Different enemies would be an idea, like in my game.
So, fixing the points above (or not if you disagree) and increasing the difficulty could make the game better. But you have a solid game. No bugs and physics are working fine.