Gameplay

Metal Gear 2 builds upon the stealth-based gameplay of its predecessor. As in the original Metal Gear, the player's objective is to infiltrate the enemy's stronghold, while avoiding detection from soldiers, cameras, infrared sensors and other surveillance devices. The biggest change in the game was done to the enemy's behavior. Whereas the guards in the original game could see in straight lines, the guards in Metal Gear 2 all have a field of vision of 45 degrees. The guards can also turn their heads left or right to see diagonally and move from one screen to another (instead of remaining stationed in one area). The enemy can also hear any noise made by the player, which usually occurs when the player knocks on a wall, fires a non-silenced firearm, uses an explosive, or walks over certain types of terrain. If the player is discovered by the enemy, then a counter will be displayed on the upper right side of the screen that will go down after the enemy has lost track of the player. When the counter reaches zero, the alert phase will go off and the game will return to normal.

The player has been given a variety of new maneuvers and tools to help them remain undetected and complete the game. For example, the player can now kneel and crawl in addition to walking, allowing the player to avoid making noise, pick up land mines, and hide under tight spaces such as under desks or inside air ducts. A radar with a 3x3 grid on the upper right of the screen shows Snake's current position in the center screen (as a red dot), with enemy soldiers as white dots, allowing the player to determine what's ahead. However, the radar is disabled when the player is in alert phase. The radar can also be used with the mine detector equipped to determine the locations of any placed mines or fire stinger missiles on an airborne target. Many of the weapons and equipment from the first game are brought over as well as new items such as robotic mice used to distract enemies, a camouflaged mat and three different types of rations with their special attributes. The player no longer needs to rescue hostages to increase their rank; instead their life energy and carrying capacity is increased each time they defeat one of the game's bosses.

The transceiver has been greatly revamped from the first game as well. The messages the player receives are now based on their current situation and mission objective, rather than the room they're currently in, making them less fixed and more dynamic. The transceiver now displays Snake's face, as well as the face of the character he's currently communicating with. The player can also talk to children living in the fortress to gain new information; the player is penalized with loss of health if he kills a child. The game's areas are more varied than in the first game and a number of puzzles must be fulfilled to complete the game, such as luring a carrier pigeon with a ration, chasing after a female spy to the women's bathroom or deciphering secret Tap Codes to gain vital information such as a new frequency number.