Undertale is an indie RPG where the player controls a human who falls into a subterranean world inhabited by monsters. The objective is to escape this world, though players can choose to remain.

The game's combat system allows for non-violent resolution through negotiation. Attacks are timed for damage, and evasion is handled like a top-down shooter. Undertale features original art and music, with a story emphasizing humor and character relationships, including the possibility of befriending bosses and dating a skeleton. The game was primarily developed by a single individual.