Library of Congress as one of the ten most important video games in history. Gameplay Zork is a text-based adventure game wherein the player explores the ruins of the Great Underground Empire. The player types text commands for their character to traverse locations, solve puzzles, and collect treasure. The game has hundreds of locations, each with a name and description, and the player's commands interact with the objects, obstacles, and creatures within them. Commands can be one or two words (e.g., "get lamp" or "north") or more complex phrases (e.g., "put the lamp and sword in the case"). The command must fit the location's context (e.g., "get lamp" works only if a lamp is present). The program acts as a narrator, describing to the player their location and the results of certain actions. If the game does not understand the player's commands, it asks for the player to retype their actions. The program's replies are typically in a sarcastic, conversational tone, much as a Dungeon Master would use in leading players in a tabletop role-playing game. The original 1977 version of the game was a single release, Zork. When it was converted into a commercial software title, it was divided into three episodes, with new and expanded sections added to the latter two episodes. Much of the game world is composed of puzzles that must eventually be solved, such as a set of buttons on a dam or a maze to be traversed. Some puzzles have more than one solution. For instance, since the "Loud Room" is too overwhelmingly loud for the player to perform actions, the player can either empty the nearby dam to stop the sound of water falling, or shout "echo" in the room to change its acoustics. In the first episode, or ZorkI, a thief character is wandering the underground as well, taking items that have been left behind or even stealing from the player's possessions. The player can fight or evade the thief, and can recover stolen items from the thief's treasure room. Some locations contain antagonists that the player must fight or overcome. Beginning in ZorkII the player can learn magic spells to use in puzzles and combat. In dark areas, the player must carry a lantern or other light source to avoid being eaten by a monster called a grue. There is a limit to how much "inventory" one can carry, determined by