http://www.youtube.c...tch?v=uErk65UgCpo

in contrast, here's the original version of Asteroids for it.
http://www.youtube.c...tch?v=JEsJJe5y8Kk

To deal with al the objects on the original version they flicker everything. One frame of video displays the ship, enemy saucer, and the player's shots. The other frame draws all the asteroids and the saucer's shots. To prevent further flicker, the asteroids move up/down at a constant rate of speed. This allows one of the two sprites to draw all the upward moving asteroids (as they never cross each other's path) while the other sprite draws all the downward moving asteroids. The only speed variation is in the left/right movement. Some game variations add additional left/right speeds, but they're still quite limited.

In my version I reuse both sprites to draw everything and only flicker if more than 3 objects occupy the same horizontal zone. I always flicker the two missiles and ball in order to draw up to 6 shots (4 for the player, 2 for the saucer)