Perhaps the most popular stealth adventure game franchise of all time celebrates its 30th anniversary this month – Metal Gear. Though the series has since expanded to include a number of sequels and spinoffs, it all began with the release of the first Metal Gear for the Japanese MSX2 computer on July 13, 1987.

The story followed a special operative going by the codename Solid Snake, who works for the special forces unit known as FOXHOUND. The unit’s commander, Big Boss, sends Snake to a place known as Outer Heaven in South Africa to investigate what happened to fellow operative Gray Fox. Snake is able to find his way into the Outer Heaven base and rescue Fox, and soon discovers the Metal Gear project: a bipedal tank that has the ability to launch nuclear missiles.

Snake is able to destroy the Metal Gear before it’s completed, but learns along the way that his own mentor, Big Boss himself, is behind the operations at Outer Heaven. Big Boss tells Snake that he sent him in, believing him to be too inexperienced to complete the mission successfully, in order to feed misinformation to western forces. Eventually, Snake takes down Big Boss in a climactic final battle and escapes Outer Heaven before the base can self-destruct.

The game was directed by Hideo Kojima, and the Metal Gear franchise has become Kojima’s best-known work. He actually took over the project from another developer at Konami; the original project was meant to be focused on combat. However, due to the MSX2’s limitations, they weren’t able to render many projectiles on screen all at once – so the focus was changed to stealth infiltration instead.

The original Metal Gear was ported to the Nintendo Entertainment System by 1988, and featured a number of changes from the original version, with different level designs being the most notable. The English localization of the NES edition also had some infamous spelling and grammar errors, such as “Contact missing our Grey Fox” and “I feel asleep!!”

A sequel, Metal Gear 2, arrived in 1990 (and there was also a non-canonical entry called Snake’s Revenge that arrived in 1990), but the series didn’t truly see significant mainstream success until the arrival of Metal Gear Solid for the PlayStation in 1998. The Metal Gear franchise is one of the best-regarded and most influential game series of all time, and (due to conflicts between Kojima and Konami) though the future of the series seems insecure, its legacy lives on.