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 run by duuuuude5, is a playaround starting from a hacked save file with the Punch Card item and a custom player name. The goal is to swap the True Pacifist and Genocide routes using a large assortment of glitches and one frame of a noclip mod to make it possible. The end result includes killing monsters during the True Pacifist route as well as freeing the underground during the Genocide route, the opposite of how the game normally plays out. Several other glitches and tricks are shown off along the way, many of which have never been seen before.