Ultima Underworld is a role-playing game that takes place from a first-person perspective in a three-dimensional environment. The player's goal is to adventure through a large, multi-level dungeon, in which the entire game is set. The player uses a freely movable mouse cursor to interact with the game's world, and with the icon-based interface on the heads-up display (HUD). Each icon has a specific effect; for example, the Look icon allows the player to examine objects closely, while the Fight icon causes the player character to ready its weapon. The player's progression through the game is non-linear: areas may be explored, and puzzles and quests finished, in any order. An automatically filling map, to which the player may add notes, records what the player has seen above a minimum level of brightness. The player character may carry light sources to extend the line of sight in varying amounts. Exploratory actions include looking up and down, jumping, and swimming.