Challenges and Bugs

There are many areas where the game can be improved. You can attempt the following in any order.

There is at least one bug in the program. Can you find and fix it? Hint: It sometimes occurs upon game over.

Multi-drones : Currently, you can only pick up one drone. Can you enhance the program so that picking up multiple strawberry donuts will give you more drones?
Shield : Can you add another power up that gives your ship a shield? The shield should disappear after blocking one bullet.
Shield+ : Enhance the shield code, so that you can pickup multiple powerups to strengthen the shield.
Bomb : Can you add a bomb power up that destroys all enemies on screen when it is picked up?

Tough Enemy : Create an enemy that takes mutiple bullets to destroy.
Shooter Enemy : Create an enemy that shoots bullets continuously in all directions.
Boss Enemy : Create a boss enemy. Research on how the boss enemy in Twin Bee behaves (...you can look at YouTube videos) for your reference.

Create a start screen for the game. The actual game should only start when you click the "Start" icon on the start screen.
Create multiple levels. You can change the background and types of enemies for each level.

Give your player multiple lives (...maybe 3 lives). The game should end only when all 3 lives are lost.

These may not affect the gameplay, but can make the game look better.