quickly and so do not give back to the project. Geitgey further noted that music and art development is not built up from the work of others in the same way that coding would be. He argued that high quality art content is required, which is typically produced commercially by paid artists. While Linux operates on the open-source philosophy, this may not benefit game development. As of September 2015, the Steam gaming service has 1,500 games available on Linux, compared to 2,323 games for Mac and 6,500 Windows games. History Beginnings and early games Just as in most other forms of software, free software was an unconscious occurrence during the creation of early computer games, particularly for earlier Unix games. These are mostly arcade conversions, parlour games, and text adventures using libraries like curses. A notable example of this is the "BSD Games", a collection of interactive fiction and other text-mode titles. Game fan communities such as the modding community do include some aspects of free software, such as sharing mods across community sites, sometimes with free to use media made for the modification. With the rise of proprietary software in the mid to late 1980s, games became more and more proprietary. However, this also led to the first deliberately free games such as GNU Chess, GNU Shogi and GNU Go of the GNU Project, part of whose goal is to create a complete free software system, games included. More advanced free gaming projects emerged, such as Moria and its descendent Angband, Hack and its derivatives NetHack and Slash'EM, in addition to Xtrek successor Netrek, variants of robots, and adventure game Dunnet, which has been included with GNU Emacs since 1994. Still developed and played today, front-ends for frameworks such as X11, SDL, GTK and Qt, plus fuller featured variants such as Iso-Angband, glHack and Vulture's Eye have kept the games accessible. Roguelikes have continued to be produced, including Cataclysm: Dark Days Ahead, Tales of Maj'Eyal, HyperRogue, DRL, Isleward, Egoboo, S.C.O.U.R.G.E., Shattered Pixel Dungeon, as well as Linley's Dungeon Crawl and its offspring Dungeon Crawl Stone Soup. The source code to the original Rogue was released under the BSD license in 1986. As PC gaming began to emerge in the late 1980s and early 1990s, free gaming also advanced. More complicated games utilizing the X Window System for graphics started to appear, most beginning with the signature letter X. These