Undertaleis a role-playing video game created by indie developer Toby Fox. The player controls a child who has fallen into the Underground: a large, secluded region under the surface of the Earth, separated by a magic barrier. The player meets various monsters during the journey back to the surface. Some monsters might engage the player in a fight. The combat system involves the player navigating through mini-bullet hell attacks by the opponent. They can opt to pacify or subdue monsters in order to spare them instead of killing them. These choices affect the game, with the dialogue, characters, and story changing based on outcomes.
Outside of some artwork, Fox developed the entirety of the game by himself, including the script and music. The game took inspiration from several sources. These include theMotherandMario & Luigirole-playing series, the bullet hell shooter seriesTouhou Project, and the British comedy showMr. Bean. Originally,Undertalewas meant to be two hours in length and was set to be released in mid-2014. However, development was delayed over the next three years.