 Complete the following phrase:  Doom 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 