It's war, and you are a gunner in a fortified gun emplacement, or pillbox. Your position at the top of the screen is slowly being over-run by soldiers, who are creeping up on you from the bottom of the screen, and taking cover behind rows of sand-bags. Once the enemy gets past the final row, they will destroy your base with a grenade, so you will need to shoot them before that happens. You control the cross-hairs of a gun, and must take aim and fire at the soldiers when they are crawling between the sandbags, which is the only time they are exposed. Occasionally, the leader of the troops briefly appears at the bottom of the screen to encourage their troops. Shooting the leader will cause all of the remaining troops to surrender, and the next wave to begin. The difficulty increases for the later waves, when the troops start crawling faster, and vehicles will sometimes appear which deliver soldiers closer to your pillbox.