Ball Wars

When I learned QBasic, this was the first game I made. When I learned Visual Basic, this was the first game I made. So, I thought, what the heck, why not make it in Java too. After spending two days learning Java, I spent another two days making this. When you compile and run, you see two balls bouncing around and a green unfilled one. Your objective is to move your green ball(by using the arrow keys) over the blue ball and press space to shoot it. If the red ball hits you, you loose a life. Because I'm just starting, I don't want to get messed im for the future, so please tell me any bad coding practices you notice.