This post originally appeared on Matt Weise's blog Outside Your Heaven.

I just finished the demo for Peace Walker, and I am struck by how streamlined its game design is compared to previous Metal Gear games. The number of core actions available to the player have been significantly reduced, at least at first glance. Some have just been made context-sensitive, while others have indeed been eliminated. Given that Metal Gear is basically a 20 year old game design, one where the core mechanics can still be traced with impressive fidelity back to the 1986 original, its interesting to chart how they've mutated over the course of roughly eight games.

Metal Gear (MSX 1986) had a fairly small set of core mechanics. The player could move, punch, and shoot various weapons. Enemies would patrol around and attack if you crossed their line of sight, which was pretty straightforward since they had no peripheral vision. Levels were simple affairs where each room was a single screen, and all level design architecture was in right angles. (There was no diagonal movement.) Escaping to the next room/screen meant escaping your pursuers. Enemies could be dispatched up-close and quietly, via punching, or from a distance and loudly, via weapons.

Metal Gear 2: Solid Snake (MSX 1990) added quite a lot of new elements. The biggest was probably the radar system, which was really several new design elements working in concert with each other. Unlike the first game, enemies in MG2 would follow you from screen to screen. Thanks to a 3x3 grid radar, the player could see which of the adjacent screens had enemies and which did not. If an enemy spotted you, they went into high alert and gave chase. If you managed to break their line of sight (usually by escaping to the next screen) they would begin searching for you. Since moving to the next screen no long constituted "hiding", new hiding mechanics were introduced. Crawling allowed you to hide under tables and sneak into air vents, which was now the only way to shake pursuers.

MG2 still contained all the same core player actions established in MG1, only now some of them were given additional meaning in the context of the new system. Punching, which before was only useful as a silent take-down technique, became a mode of distraction. You could punch walls to make noise, which would lure enemies towards you. This example of appropriating old mechanics and given them new meaning in the context of a larger dynamic system is primarily what makes Metal Gear an interesting case-study, an on-going game design matryoshka in which each new design encapsulates the last but still manages remain a distinct experience.