Hi,

I think your game works so far, simple and efficient.
If you want to improve it, i was thinking of a few things:

- Spontaneously I would have liked using space bar rather than left key to fire, but it may be personal. Maybe allow both?
- What could improve the challenge would be a negative feedback loop: the more your score raises, the more difficult it is to survive. But blindly raising enemy speed won't make it, I think. Maybe cubes of different colors with some specific skills, appearing for example at score 100? I was thinking of a cube with varying level of transparence over time, so that you see it and it disappears, and it appears again. It forces you to anticipate.

Good luck in your development!