Star Fortress

Star Fortress is a 1-player arcade game for the TRS-80.

The player controls a spaceship that moves horizontally and fires vertically upwards. A large alien hides behind 4 layers of alternately scrolling shields. The player tries to shoot out the shields to destroy the alien behind. Alien defense systems continuously fire towards the player, and if the alien aligns with open shields, it will also fire through the defense system. If the lowest level of shields is overly damaged, a new level of shield forms, and the shield levels are shifted downwards. The player starts with 3 lives, and gains a life and 500 points for every alien destroyed. There are 5 levels of difficulty.