Metal Gear 2: Solid Snake

Metal Gear 2 builds upon the stealth-based gameplay system 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 abilities. Instead of remaining stationed in one screen like in the first game, enemy soldiers can now patrol different screens across a single map.

Moreover, guards now have an expanded 45-degree field of vision instead of just seeing in straight lines, along with the ability to turn their heads left or right to see diagonally. Enemy guards can also detect sounds, being able to hear any noise made by the player (such as a punch to the wall or a gunshot made without a suppressor) and will investigate the source of the sound once it is made. Guards can also hear sounds made by the player when walking on certain surfaces, which means that one has to be careful when navigating certain areas. 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.

Metal Gear 2 is set in a near-future world in which the Cold War continued into the 1990s, with the game's events taking place in 1999, three years after the events of the original Metal Gear (later retconned to four years in Metal Gear Solid).

Solid Snake, formerly retired FOXHOUND agent and hero of the original Metal Gear returns as the playable character. His new mission is to rescue the kidnapped Czechoslovak biologist Dr. Kio Marv from the forces of Zanzibar Land. He is assisted by a radio support crew consisting of Roy Kyanbel (spelled "Roy Campbell" in later versions), his new commanding officer; McDonnell Miller, a survival coach and drill instructor; George Kesler ("George Kasler" in later versions), a military strategist; and Yozev Norden (renamed Johan Jacobsen in the later revised versions), a wildlife expert.

Following the success of the NES version of Metal Gear, which sold over a million units in North America, Konami began the development of a sequel for the same platform titled Snake's Revenge designed specifically for the overseas market. Hideo Kojima, who directed the first MSX2 game but was not involved with either of the two NES games, did not have any plans to develop a sequel himself at the time until he became reacquainted with a junior coworker who was assigned to work on Snake's Revenge on a train ride in Tokyo. The coworker revealed his involvement with the project and encouraged Kojima to create his own sequel. By the end of the train ride, Kojima had already envisioned the basic premise for the game. After undergoing a business trip to the sales division of Konami, Kojima successfully convinced his superiors, who were hesitant to develop a Metal Gear sequel for the Japanese market due to poor sales of the Famicom conversion of the first game, to approve the development of Metal Gear 2: Solid Snake.

In order to accurately portray realism in the game, Kojima and his crew consulted various references, including a former Green Beret turned author, and even participated in a series of survival games in a forest located in a mountain near their workplace. Originally Metal Gear 2 was announced with a February to March 1990 release window, but was delayed to July, undergoing an increase in ROM size from 3 megabits to 4 megabits. Metal Gear 2 also employs Konami's proprietary SCC sound source that has been used in all of their MSX titles since Nemesis 2. Development of Metal Gear 2 was briefly suspended in order to help out on the development of SD Snatcher, which was being developed at the same time by a separate team.

During its initial release, Metal Gear 2 was ranked on MSX Magazine's Top 30 best-selling MSX games list for six months, premiering at the No. 1 spot on the October 1990 issue. Metal Gear 2: Solid Snake would later receive near universal-acclaim by retro game reviewers. According to Paul Soth of GameSpy, the game surpassed its predecessor Metal Gear in every way.

In addition to praising the gameplay, he also praised the game's "gripping, well-written storyline" for its "rich characterization" and its "same quality of storytelling that made MGS so compelling." He concluded that players will not be disappointed by "the great gameplay and story," and that it remains "one of the best 8-bit games ever made." Game Informer was more critical of the game, however, giving it a 7 out of 10. They wrote that in order to reach the most pivotal moments in the game's story, "you must endure some of the most ridiculous situations Solid Snake has ever seen," and that "the game's focus on constant backtracking and keycard acquisition makes it too repetitive."