On October 30, 2018, Fox tweeted a request for fans of Undertale to check the game's official Twitter account in 24 hours. The following day, Fox released the first chapter of the followup to Undertale, named Deltarune, for free under the guise of a "survey".[28][29] On November 1, Fox shared more details regarding the game, including that the rest of the chapters were expected to release simultaneously, but work had not yet started, and there was no estimated timeframe for completion.[30] Fox also stated that he had been working on the project since 2012, and that the idea for Undertale developed from Deltarune during production.[30][31] On June 12, 2019, as only the first chapter of Deltarune had been playable for several months, Fox expressed on his Twitter account he had hope he would complete the rest of Deltarune, saying: "Slowly I'm writing and drawing it all out."[32] He stated that he has written "about 50 songs past Chapter 1".[33]