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The game adopts certain play mechanics from Metal Gear Solid 4, such as the crouching walk, the over-the-shoulder shooting view, the CQC system, and the ability to search held-up soldiers.
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Players can replay previously cleared missions for higher scores. A player's score is penalized with a lower rank and reduced heroism for excessive killing and frequently being discovered, whereas players who are stealthy and subdue enemy soldiers non-lethally will be awarded appropriately. When the player completes a mission, their performance is evaluated afterward. Extra Ops are optional missions that involve much more elaborate goals ranging from simple target practices to obtaining secret documents. Some Main Ops missions include illustrated cutscenes that involve bits of interactivity in order to proceed. There are two main types of Missions: Main Ops are the primary story-based missions in which goals are determined by the narrative and must be played in a strict order in order to proceed. Players get to choose which missions to play from the "Mission Selector" screen. "Mission" are the actual action sequences of the game, where the player must infiltrate an enemy territory or fight a boss, whereas "Mother Base" is an army management mode similar to the briefing screen in Portable Ops. Peace Walker consists of two primary gameplay modes: "Mission" and "Mother Base". The player's partner is barely seen hiding on the other side of the truck. The image has Snake in Naked uniform hiding from a Peace Sentinels soldier, armed with an M60 GPMG. Snake and an MSF soldier conducting a Co-Ops mission.
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The game received critical acclaim, but the PlayStation Portable version failed to match the commercial success of its console predecessors due to declining support for the system.
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Peace Walker is set in Costa Rica in 1974, and follows the exploits of returning protagonist Snake as he runs the mercenary unit Militaires Sans Frontières (Soldiers Without Borders). The game was later released for the PlayStation 3 and Xbox 360 as part of the Metal Gear Solid HD Collection in North America and Europe and as a stand-alone retail release in Japan. It is the seventh Metal Gear game written, directed, and designed by Hideo Kojima, and the fifth installment of the Metal Gear Solid series, as well as the fourth Metal Gear game made specifically for the PlayStation Portable, following Metal Gear Solid: Portable Ops. Metal Gear Solid: Peace Walker is a 2010 stealth game developed by Kojima Productions and published by Konami.
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