As games became more realistic, issues of questionable content arose. The most notable early example is "NARC", which through its use of digitized graphics and sound and its adult-oriented theme quickly became a target of the press. These same issues arose again when "Mortal Kombat" debuted, particularly with its home video game console released on the Genesis and Super NES platforms; due to Nintendo's strict content-control guidelines, that system's version of "Mortal Kombat" was substantially re-worked to remove any 'extreme' violence. In response to these issues (and in parallel to similar demands made upon the music and movie industries), the ESRB was established to help guide parents in their purchasing decisions. 1993's "Doom" caused quite a stir, with its detailed 3D graphics and copious amounts of blood and gore. The 1996 game, Duke Nukem 3D, was accused of promoting pornography and violence; as a result of the criticism, censored versions of the game were released in certain countries. In the 1999 Columbine shootings, violent video games were for a time directly blamed by some for the incident, and labeled as "murder simulators".