Hi Star,
I have few more suggestions but it's ok if you dont want to include this yet in your release :
1. Improve enemy bullets. It's a little darker on my h1910 with max backlight. Maybe a blue plasma ball or yellow will do.
2. The bullet timing (enemies) must be synchronized. So that the player can play against the bullet/reload fire timing. Meaning the ship can go under the enemies while they are reloading. Right now I 'assume' that your bullet fire is random
3. Just a though of firing sideways (power ups). I cant shoot the enemy with the ship level or it's near the ground.
4. Add power ups for stronger bullets/fire.
Goodluck

It's worth the wait...