Press space to fire ball. Hold to let it stay. Let go for it to disappear. Play with the sliders. Use arrow or W-A-S-D keys to move cannon.
I was bored, and then I made this. This isn't even close to realistic. 0.7: Removed Magnet Mode, it was to stupid and glitchy. 0.6.2: Ball doesn't glitch out when hitting the floor. 0.6.1: Ball bounces on the floor now. 0.6: Added a magnet mode. 0.5: Added movable cannon and particles. 0.4.1: Ball loses energy when bouncing. 0.4: Added bouncing. 0.3: Added ability to toggle speed and gravity. 0.2: Added gravity. 0.1: Added a cannon, and a ball.