Gameplay
In single player, players explore and navigate to the exit of each level, facing many challenging monsters and a few secret areas along the way. Usually there are buttons to press or keys to collect in order to open doors before the exit can be reached. Once reaching the exit, the game takes the player to the next level.
Before the start level, there is a set of three pathways with easy, medium, and hard skill levels; in order to reach the Nightmare skill level (described in the game manual as "so bad that it was hidden, so people won't wander in by accident"), the player must drop through the water before the Episode 4 entrance and jump into a secret passage.
Quake's single-player campaign is organized into four individual episodes of about eight levels each (each including a secret level, one of which is a "low gravity" level—Ziggurat Vertigo in Episode 1, Dimension of the Doomed—that challenges the player's abilities in a different way). As items are collected, they are carried to the next level, each usually more challenging than the last. If the player dies, he must restart at the beginning of the level. However, games may be saved at any time.
Upon completing each episode, the player is returned to the hub Start level, where another episode can be entered. Each episode starts the player from scratch, without any previously collected items. Episode I (which formed the shareware or downloadable demo version of Quake) has the most traditional ideology of a boss in the last level. The ultimate objective at the end of an episode is to recover a magic rune. After all of the runes are collected, the floor of the Start opens up to reveal an entrance to the End level which contains the final boss, based on the god Shub-Niggurath from the Cthulhu Mythos.
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