Colossal Cave Adventure is a text adventure game, developed originally in 1976, by Will Crowther for the PDP-10 mainframe. The game was expanded upon in 1977, with help from Don Woods, and other programmers created variations on the game and ports to other systems in the following years. In the game, the player controls a character through simple text commands to explore a cave rumored to be filled with wealth. Players earn predetermined points for acquiring treasure and escaping the cave alive, with the goal to earn the maximum amount of points offered. The concept bore out from Crowther's background as a caving enthusiast, with the game's cave structured loosely around the Mammoth Cave system in Kentucky.