Galaga 1990

[Geoff Canyon Rev]

You definitely don't want to do this by positioning everything every
time you update. Instead, the move command is your special friend
here. For the enemy, you can plot out a randomized course from the top
to the bottom, and then tell it to follow that path in a set amount of
time. The bullets are even easier since they just have to go from
bottom to top. I did a quick hack job, cutting the code about in half
and speeding it up significantly. It now handles three enemies and 11
bullets without breaking a sweat on my macbook. Here's the stack:
http://snurl.com/wsclc and here's the article I posted with some
comments: http://gcanyon.posterous.com/a-blast-from-my-programming-past