MPO is the fourth Metal Gear title made specifically for the PSP and the first one to retain the series' action-based play mechanics. It is the first canonical outing of the Metal Gear Solid series for a portable platform, following the storyline of Metal Gear Solid 3: Snake Eater. Set in Colombia in 1970, six years after the events of Snake Eater, the game follows the exploits of Naked Snake after his former unit, FOX, goes renegade. The game also chronicles the eventual founding of FOXHOUND and The Patriots, as well as the inspiration of the military state Outer Heaven. Metal Gear Solid: Portable Ops has received highly positive critical reception from critics, and is often viewed as one of the best games released for the PSP. It was praised for its visuals, usage of Metal Gear elements and story, while criticism was directed at the game's control scheme.