You've done all the required steps, but if you'd like to make the project your own, here are some ideas:
- Add types
- Add a scoring system
- Implement multiple lives and respawning
- Add an explosion effect for the asteroids
- Add acceleration to the player movement
- Make the objects wrap around the screen instead of disappearing
- Add a background image
- Create different weapon types
- Make the asteroids lumpy instead of perfectly round
- Make the ship have a triangular hit box instead of a circular one
- Add a shield power-up
- Add a speed power-up
- Add bombs that can be dropped