Indecent

Indecent packs an arcade flying game with 256 different levels, parallax scrolling, and procedurally generated terrain, into the rather tight space of 256 bytes of machine code. The idea is to get your starship safely across an increasingly dangerous environment, plagued by floating junk (yellow dots) and by cave walls that gradually start closing in the further you travel. The white, pixelly ship can only be moved up or down to avoid these obstacles - any collision spells instantaneous doom; a progress bar at the bottom tells you how much of the level you've traveled. Various levels may be loaded by specifying different ASCII characters as a command-line parameter.