Escape from the Planet of the Robot Monsters
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The name sounds like a 50s B-movie, and that's pretty much what the game plays like, as well. Two players take on the role of square jawed space heroes who fight wave after wave of evil robots in their attempt to free humans enslaved by the evil Reptilons. Schlocky and a bit exploitative, the game was a good time, though the absolutely brutal difficulty level meant you needed to use a whole pocketful of quarters to see the ending. All told, it's a memorable, unusual and very interesting Co-Op Classic.