In MGS4, the player must navigate the game world in order to progress. Unlike the other Metal Gear games, where Solid Snake is youthful and agile, the more elderly version of Snake has a more difficult time employing stealth, so he focuses more towards eliminating the targets rather than sneak around them. It will use the series' traditional third person view with full camera manipulation, but also allows the freedom to play in first-person mode, as well as an over the shoulder view which can be switched from right shoulder to left for easy corner maneuvering. The Close Quarters Combat system will be completely revamped. The player will also be able to interrogate guards for information and supplies.
Several elements from previous titles return in modified forms. Players will also use a new form of camouflage called "Octocamo", which replaces the camouflage system featured in MGS3 and the Stealth Camouflage seen in MGS and MGS2. Dark blue when disabled, the Octocamo suit allows the wearer to blend in with any surface within a few seconds. A new monocular device called "Solid Eye" replaces the various binoculars and image intensifiers from previous titles, and a steel drum compliments the series' traditional cardboard box disguise. It is able to deflect bullets, and can be rolled to knock enemy soldiers over.
According to Ryan Payton, the game will be filled with cut-scenes that explain what happened in Metal Gear Solid 1, 2, and 3, and then Portable Ops, how that relates to MGS4, and how that relates to the final chapter of Solid Snake. Although informative enough to excite the hardcore fans of the series, the cut scenes will be straight forward enough for mainstream gamers.
Snake will also be partnered with a robotic drone, the Metal Gear Mk. II, which allows him to communicate with other characters, in addition to the Codec radio system from previous games. It is also capable of engaging enemies using an electric shock, as well as providing reconnaissance. This drone is reminiscent of Gillian Seed's robotic sidekick Metal Gear Mk. II from the game Snatcher.
Due to the lack of a rumble feature during much of the PlayStation 3 development the game has been designed with a new feature: a white "Threat Ring" that visibly vibrates when sound is made nearby. As one of the first major games to make use of the DualShock 3's force feedback capabilities in a series known for extensive use of rumble,, Kojima has stated that if the feature were to be implemented, the Threat Ring may be removed.
Snake's health will play some factor during gameplay. If injured on the battlefield, cuts and burns will remain on his skin. However, the developers wish to avoid putting the stress of Snake's health to the players, so he wears a muscle suit, allowing players to move in a similar fashion to previous games.
Other changes that were announced included the new "Psyche Meter" which will replace the stamina meter from previous Metal Gear games. This Psyche Meter functions as a normal human's adrenaline meter. If you are combat, then the meter will alter, and Snake can fire rounds off faster and recieves less damage. However, if you are near something that smells bad, then the meter will change again, and Snake will move slower and slightly awkward. The "Baseline Map" is a radar map with a dynamically resized circle based on Snake's "presence" to the environment.
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