Step One: Watch Mary Rose Cook Live Codes Space Invaders from Front-Trends. (The second worst conference name ever?)
Step Two: Fork this gist.
Step Three: Respond to this question in your fork: What is one approach you can take from this Mary's code and implement in your project?
One approach that I can take is the update method. I'm currently experiencing the same problem in snake, where the snake is just drawing every box that it knows about and is never clearing them. So I think I can use Mary's update method to solve that issue...or maybe I'll just make Tron instead :)
Step Four: Totally Optional: take a look at some of the other forks and comment if the spirit moves you.
When a bad a snake becomes a good tron.........