Toby Fox (born October 11, 1991) is an American video game developer and composer. He is best known for developing the games Undertale and Deltarune. He has also composed music for the webcomic Homestuck, as well as for the video games Hiveswap, Escaped Chasm, Little Town Hero, Pokémon Sword and Shield and Super Smash Bros. Ultimate. He is also known online as FwugRadiation or as Toby "Radiation" Fox.