For years, little content from "X-treme" was released beyond promotional screenshots. In 2006, a copy of an early test engine was sold at auction for US$2500 to an anonymous collector. An animated GIF image of gameplay was released, and after a fundraising project by the "Assemblergames" website community purchased the disc from the collector, the disk image was leaked on July 17, 2007. Senn opened the ""Sonic X-treme" Compendium" website and revealed large amounts of development history, including early footage, a playable character named Tiara, and concept music. Senn considered finishing "X-treme" himself, and used some of its concepts in a "Sonic" fan game. In February 2015, fans obtained the "Sonic X-treme" source code and created a playable build.