Reverse Engineer updated his Atari 7800 game Time Salvo, which is an update on the classic computer game Crossfire.

Shoot the enemies, and avoid being shot. After some time passes in the level, humanoids will begin appearing. Your enemies will kill the humanoids if they touch them, but if you run into the humanoids they will follow you. Keep them safe until the end of the level. Periodically you will need to refuel on ammunition. An alarm will sound, and you’ll see the ammunition on the playfield. Run across the ammunition to pick it up. Every 2 rounds you will reach the challenging stage, where 4 waves of enemies will race across the screen in patterns. If you shoot all 44 enemies you will earn an extra life.

http://atariage.com/forums/topic/224469-salvo/