"Doom" was notorious for its high levels of graphic violence and satanic imagery, which generated controversy from a broad range of groups. "Doom" for the Genesis 32X was one of the first video games to be given an M for Mature rating from the Entertainment Software Rating Board due to its violent gore and nature. Yahoo! Games listed it as one of the top ten most controversial games of all time. It was criticized by religious organizations for its diabolic undertones and was dubbed a "mass murder simulator" by critic and Killology Research Group founder David Grossman. "Doom" prompted fears that the then-emerging virtual reality technology could be used to simulate extremely realistic killing.