1. Modify your solution to #8 so that if an ellipse is touched by the mouse, it turns permanently green.Bonus (up to +5): a green ellipse stops moving, but recovers after 5 seconds, returning to its old color and regaining its ability to move.
2. Implement a "lunar lander" simulation. The lander will fall according to gravity, but by firing the rockets (press spacebar) you can slow its fall (accelerate upwards). If the lander touches the ground with less than a certain speed, it landed safely, otherwise it crashed.
Bonus (up to +3): allow rockets to fire side to side also, and have a "safe landing" zone, where landing outside the safe zone counts as a crash.