oom has been considered the most important first-person shooter ever made. It was highly influential not only on subsequent shooter games but on video gaming in general, and has been made available on almost every video gaming system since. Multiplayer gaming, which is now integral to the first-person shooter genre, was first successfully achieved on a large scale by Doom. While its combination of gory violence, dark humor and hellish imagery garnered acclaim from critics, these attributes also generated criticism from religious groups and censorship committees, with many commentators labelling the game a "murder simulator". There was further controversy when it emerged that the perpetrators of the Columbine High School massacre were fans of the game; the families of several victims later unsuccessfully attempted to sue numerous video game companies - among them id Software - whose work the families claimed inspired the massacre. Ri
se of the Triad was released almost exactly a year later, on December 21, 1994. Based on a very heavily modified Wolfenstein engine, it did not feature Doom's variable-height ceilings or diagonal walls. However, various powerups and environmental features gave players the ability to fly or be launched through the air, and its use of GADs (Gravitational Anomaly Devices) provided staircases and a primitive form of rooms over rooms, both which Doom lacked. ROTT would become Doom's biggest competitor on the PC platform. In the same month, Marathon was released for the Macintosh. Its engine's capabilities were extremely similar to those of the Doom engine, but it featured a few improvements like mouselook and rooms over rooms in addition to a more sophisticated story. It was one of the earliest shooters, if not the earliest, to utilize alternate fire modes, reloading magazines, and dual-wieldi
