The screen display is a field of diamonds on which are four robots...Any robot can pick up diamonds for any player.
The players take turns moving the robot of their choice. You get one point for each diamond picked up, and the high score wins. The robots move in the eight [cardinal] directions.
If you want the computer to play in a multiplayer game, type COMPUTER when the game asks for the name of a player.
Mercury Mine was written by Sol Guber and published as type-in source code in Creative Computing Vol. 9, No. 5, May 1983