Players control Snake through the game map and attempt to complete missions while avoiding being spotted by the enemy. The threat detection system is revamped, with the removal of the onscreen meter or gauge to indicate the player that they are in the 'alert/evasion/caution' state as in previous games, which have instead been replaced by visual and audio representations. Snake's binoculars have been revamped; instead of selecting the binoculars as an item, the binoculars are hot keyed to a button. The player is able to mark enemies and be aware of their locations in the iDroid's holographic display. There are directional cues to help players when an enemy sees them from a distance and gets closer to them. A new "Reflex Mode" is activated when an enemy finds Snake and the player only has a short window of time to take out the enemy before they fully sound the alarm. Lights can be shot out to further aid the player's stealth efforts.[1]
Ground Zeroes features seven missions in total,[2][3] locked at individual levels. After completing the main mission the player unlocks four subsequent missions (referred to as "Side Ops") set at different points in the day, all set in Camp Omega. These missions involve specific tasks, such as eliminating certain targets or obtaining classified information. After achieving a certain objective in the main mission, the player may unlock two additional "Extra Op" missions.[4]
As the game is introductory in nature, being a prologue, the core story mission can be completed in a very short time frame.[5] However, the game has many additional challenges, missions and alternative methods of play.[6] A companion app for iOS or Android was made to help players access the in-game map and other iDroid functions on their smartphones. Console versions of the game have community features that allows a player to look at other players' performance in the game, showing where they were killed on the map.[7][8]
Atmospheric weather and lighting in Ground Zeroes is mission-proprietary, meaning that the setting of the game depends on the individual mission being played. A real-time day and night cycle was originally planned for the game, but left out in favor of fully utilizing it in The Phantom Pain.[9][10] Kojima has spoken about the restrictive nature of previous Metal Gear titles, saying that they "set [the player] on one rail to get from point A to point B, with a certain amount of freedom between". In contrast, Kojima's team instead offered the player new ways of traversal and sneaking methods, such as taking a jeep, a car, or a helicopter around the mission area. This was in order for Kojima to accomplish a "true open world experience" with Ground Zeroes.[11]
