Touhou Project has become particularly notable as a prominent source of Japanese dōjin content, with the series spawning a vast body of fan-made works such as artwork, music, print works, video games, and Internet memes. Because of this, it has gained somewhat of a cult following outside of Japan. The popularity of the series and its derivative works has been attributed in part to the few restrictions placed by ZUN on the use of his content. Unofficial works are frequently sold at fan conventions, including Comiket, where the franchise has frequently held the record for circle participation, and the official convention Reitaisai, where trial versions of the official games are typically distributed prior to release.