multiplayer online role-playing game Urban Dead, a free grid-based browser game where zombies and survivors fight for control of a ruined city, is one of the most popular games of its type. DayZ, a zombie-based survival horror mod for ARMA 2, was responsible for over 300,000 unit sales of its parent game within two months of its release. Over a year later, the developers of the mod created a standalone version of the same game, which was in early access on Steam, and so far has sold 3 million copies since its release in December 2013. Romero would later opine that he believes that much of the 21st century obsessions with zombies can be traced more towards video games than films, noting that it was not until the 2009 film Zombieland that a zombie film was able to gross more than 100 million dollars. Outside of video games, zombies frequently appear in trading card games, such as Magic: The Gathering or Yu-Gi-Oh! Trading Card Game (which even has a Zombie-Type for its "monsters"), as well as in role-playing games, such as Dungeons & Dragons, tabletop games such as Zombies!!! and Dead of Winter: A Cross Roads Game, and tabletop wargames, such as Warhammer Fantasy and 40K. The game Humans vs. Zombies is a zombie-themed live-action game played on college campuses. Writing for Scientific American, Kyle Hill praised the 2013 game The Last of Us for its plausibility, basing its zombification process on a fictional strain of the parasitic Cordyceps fungus, a real-world genus whose members control the behavior of their arthropod hosts in "zombielike" ways to reproduce. Despite the plausibility of this mechanism (also explored in the novel The Girl with All the Gifts and the film of the same name), to date there have been no documented cases of humans infected by Cordyceps. Zombie video games have remained popular in the late 2010s, as seen with the commercial success of the Resident Evil 2 remake and Days Gone in 2019. This enduring popularity may be attributed, in part, to the fact that zombie enemies are not expected to exhibit significant levels of intelligence, making them relatively straightforward to program. However, less pragmatic advantages, such as those related to storytelling and representation, are increasingly important. American government On 18 May 2011, the United States' Centers for Disease Control and Prevention (CDC) published a graphic novel entitled Preparedness 101: Zombie Apocalypse,