Undertale is an RPG video game created by American indie developer Toby Fox in 2015.

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.

This game has a sort of newgame+ mode where, depending on when the player resets a play-through, certain story events will appear different. This TAS uses the fastest combination of those differences while also completing the neutral ending.