"System's Twilight: An Abstract Fairy Tale is a graphical interactive fiction computer game created by Andrew Plotkin in 1993. The game is a combination of puzzle and story, combining several different kinds of logic puzzles and word puzzles. The puzzles include variations of Set and Black Box, as well as many others. The overarching story is an allegory in which the player and other characters are programs in a broken, dysfunctional computer environment. Originally, Plotkin released System's Twilight as shareware. Since 2000, it has been re-released as binary-only freeware. It runs only on the Mac OS Classic environment, but can be run in emulation on other platforms." Source: Wikipedia, "System's_Twilight," available under the CC-BY-SA License.