nicknamed its early games in relation to Zork, such as "Zork: the Mystery" (Deadline, 1982), "Zorks in Space" (Starcross, 1982), and Zork IV (Enchanter, 1983). By 1986 this had increased to 26 total titles. Although Wishbringer: The Magick Stone of Dreams (1985) was ostensibly set in the same world as Zork, the company had not made any more official Zork games, releasing only a Zork Trilogy compilation of all three episodes. In 1985 Infocom diversified into professional software by creating a relational database product called Cornerstone. Poor sales led to financial difficulties and the company was sold to Activision in 1986. Infocom then created two more Zork games: Beyond Zork: The Coconut of Quendor (1987), which added a graphical map and more role-playing and combat elements, and Zork Zero: The Revenge of Megaboz (1988), a prequel game that added graphical elements and menus as well as graphical minigames. Infocom's tenure under Activision was rocky, and rising costs and falling profits, exacerbated by a lack of new products in 1988, led Activision to close Infocom in 1989. Activision returned to the series with several graphic adventure games: Return to Zork (1993), Zork Nemesis: The Forbidden Lands (1996), and Zork: Grand Inquisitor (1997). It also released Zork: The Undiscovered Underground (1997), a free text adventure game partially written by original Infocom implementers Michael Berlyn and Marc Blank to promote Zork: Grand Inquisitor. In 2009 Jolt Online Gaming released Legends of Zork, a freemium browser-based online adventure game. The original Zork games have been re-released in several compilations since Zork Trilogy. They are included in The Lost Treasures of Infocom (1991), Zork Anthology (1994), Classic Text Adventure Masterpieces of Infocom (1996), and Zork Legacy Collection (1996). A graphical port of ZorkI for the PlayStation and Sega Saturn consoles was developed by Arc System Works and published by Shōeisha in Japan in 1996, nineteen years after its original release. Unofficial versions of Zork have been created for over forty years for a wide range of systems, such as browsers or smart speakers. Four gamebooks, written by Infocom developer Steve Meretzky and set in the Zork world, were published in 1983–1984: The Forces of Krill (1983), The Malifestro Quest (1983), The Cavern of Doom (1983), and Conquest at Quendor (1984). These books, known collectively as the "Zork books", are presented as interactive fiction in the style of the Choose Your Own Adventure series, wherein the