See Vermillion Coronatus for further information.
The ending reveals that the whole battle was just a game which Case and Anna were playing, as Case raises his arm in a triumphant pose in front of the cabinet, Anna lies down on the floor begging for one more chance. If the ending is reached with both players in the game, Case and Anna will be posing triumphant shouting "We are champion!".
The ending is a reference to the Zone Y ending of Darius.