Alien

Alien is a 1-player Space Invaders game for the TRS-80.

You are alone on a planet that has just been claimed by your Federation. You have been left alone to defend it until colonists arrive. After a couple of days of quiet monitors, something appears on your comp-scan: An entire fleet of alien star destroyers - heading your way. Springing from your chair, you flip a few switches to activate the force field. The force field covers most of the planet, but not directly over the armory, creating a window for invading aliens to slip through.

The player controls a missile which moves horizontally along the bottom of the screen and fires vertically. Alien waves move as a group, and when they reach the edge of the screen, they move down one level and alternate direction. Within the armory are 4 missile launchers, and if one is destroyed, a new one takes its place. One replacement missile launcher is constructed at the end of an alien wave up to 4. Each alien wave arrives one level lower than the preceding fleet, and the player has time to repair their defensive barrier between waves. The game ends when an alien breaks through the armory's barrier line or all 4 missile launchers are destroyed. There are 3 levels of game speed.