Deltarune: Chapter 1 (stylized as DELTARUNE: Chapter 1) is a free 2D deliberately-retro fantasy RPG developed and released digitally by tobyfox for the PC and Mac on October 31, 2018. It will be ported by 8-4 to the Nintendo Switch (on February 28, 2019) and PlayStation 4 (sometime in 2019).
A spin-off of the developer's earlier game Undertale (of which the game's title is an anagram of), Deltarune: Chapter 1 takes place in an alternate universe where monsters and humans live in peace on the world's surface. Players control a human student (and silent protagonist) known as Kris, as they and a fellow classmate (the delinquent Susie) are pulled into the mysterious "Dark World", where they must prevent one of the realm's four kings from disrupting the balance between light and dark (with the aid of Ralsei, a friendly prince of darkness).
The game features a turn-based RPG system similar to Undertale, where fighting is an optional choice and players can find ways to resolve each enemy encounter peacefully (while avoiding enemy attacks by maneuvering their heart-shaped SOUL). New mechanics include a party-based system and the Tension Point system (where the group gains TP by defending themselves, giving them the ability to cast unique spells).