Pill Box

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.