Outside of artwork and character designs by Temmie Chang, Fox developed the entirety of the game by himself, including the script and music.

These choices affect the game, with the dialogue, characters, and story changing based on outcomes. They can opt to pacify or subdue monsters in order to spare them instead of killing them. The combat system involves the player navigating through mini- bullet hell attacks by the opponent. The player meets various monsters during the journey back to the surface, although some monsters might engage the player in a fight. The player controls a child named Frisk who has fallen into the Underground: a large, secluded region under the surface of the Earth, separated by a magical barrier. Undertale is a 2015 2D role-playing video game created by American indie developer Toby Fox.