Cool game, the visuals are nice and the movement is tight. Some suggestions:
- Reduce the screen shake, it's a bit too much
- The "x enemies left" should show how many enemies are needed to complete the wave, not how many are alive.
- Make enemies unable to appear near the player
- Add some music and upgrades to make it more interesting (I understand this is difficult in such little time)
Overall a good job, keep it up!