This is my 2D shooter game. I made the following modifications:

I added a instructions page
I added a parallax effect to make it an infinite game
Black holes are spawned at pre-determined distances or by time
Each black hole spawns enemy ships
Player has a health and ammo bar
Player health can be affected by bullets fired by the enemy or by hitting the enemy ship
Both health and ammo bar are refilled over time
There is also ammo refill items the player can pick up to recharge
The player has 3 lives
The UI displays the enemies to defeat and the enemies killed; player lives plus the health bar and ammo bar
Have Fun!

Credits: Duarte Teixeira