Invasion Orion is the sequel to Starfleet Orion. Like its predecessor, it is a turn-based science fiction strategy game, depicting battles between fleets of space ships. This time, the Stellar Union must fend off an invasion by the robotic Klaatu.

The primary difference between Invasion and its predecessor is that the sequel was designed for one player. In fact, on original release, the game included only a single-player mode, but later versions added a two-player option as well. When playing against the computer (who can be set to control any side), the player can choose from three difficulty levels.

Besides the required number of players, the game mechanics have remained the same as in the original: the battles take place on a 32 x 64 grid, and an encounter ends when one side's ships have been destroyed or left the battlefield. Weapons and equipment have also remained the same: short-range beams, long-range missiles and torpedoes, deployable fighter squadrons and tractor beams. One change from the original is that tractor beams can no longer be used on enemy missiles.

The game includes 10 scenarios, featuring 30 different ship types (up from 22 in Starfleet). As in the original, the scenarios have to be typed into the scenario editor for the tape versions, while the disk versions include the scenarios as finished files. The editor can not only be used to create new scenarios, but also to design entirely new ships.

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