Mountain King is a platform game for the Atari 2600, where the player assumes the role of an explorer in search of a diamond mine and the temple of an ancient civilization. The objective is to discover and collect the Golden Crown and take it to the summit of the mountain.
The mountain environment is composed of platforms and ladders, with the Perpetual Flame located at the top. The Golden Crown can only be retrieved after collecting one thousand points. Diamonds are worth 25 points each, and treasure chests are worth 260 points. Diamonds are scattered throughout the level, and treasure chests can be found using the explorer’s flashlight to navigate the darkness. While exploring the bottom of the mountain is not required, there are numerous treasure chests to discover. However, a giant spider lurks at the lowest level, and will pursue the player if they linger too long. Once the player has enough points, they must locate the Flame Spirit by following musical cues, which unlocks the Temple Chamber where the Crown is kept. However, the Skull Spirit guarding the entrance will prevent the player from entering without the Flame Spirit. When the Crown is collected, it must be taken to the Perpetual Flame, while Cave Bats now hunt the player. If the Bats touch the Crown, it will be stolen, and the player must collect points again.
The game can end in three ways. Firstly, the timer expiring. Secondly, the giant spider catching the player and trapping them in a web cocoon. The player can escape by moving the joystick left and right quickly. If the player does not escape in time, the game ends, and the player is assumed to have been eaten by the spider. Finally, if the player touches any regular fires, they will die, and the game ends.