Space Dungeon is the Atari 5200 conversion of the cooperative arcade game developed by Atari in collaboration with Taito, in which one or two players roam a series of maze-like space rooms, firing at enemies and using a radar to orient themselves on the map.
It's an early example of the shooting-with-exploration-in-connected-maps formula, a conceptual precursor to structures that would become popular later in the action-adventure genre.

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