 * ASCII art logo.
 * Decide if it's safe to delay and do so sometimes to save CPU.
 * Fix 9-13-6-2 difficulty.
 * Color @, #, and . differently.
 * Allow color themes to change the color of the train.
 * Add more color themes, using all 256 available colors.
 * Add more music tracks.
 * Use several colors for squirrels, not just red.
 * Difficulty ratings.
 * An intermission screen.
 * Optimize saturate() and/or add an option to turn it off.
