The Master Chief Collection originally consisted of Halo: Combat Evolved Anniversary, Halo 2 Anniversary, Halo 3, and Halo 4, complete with their full catalog of extras, including all multiplayer maps and gameplay modes.[3] There have been no story or gameplay changes to the original releases.[4] The games are first-person shooters with vehicular combat that takes place from a third-person perspective. Each campaign has four difficulty levels and access to gameplay modifiers known as "Skulls".