The Marathon Trilogy is a science fiction first-person shooter video game series from Bungie, originally released for the Classic Mac OS.

Taking the role of a security officer equipped with energy shields, the player makes use of various firearms in an attempt to kill their opponents while trying to avoid getting hit by enemies' attacks.

Single-player level objectives can include exterminating all hostile creatures, rescuing civilians, retrieving certain items, or exploring certain locations.

Some levels present players with simple puzzles where the objective is to find the correct switches to advance or to carefully traverse platforms.

The motion sensor tracks the movements of nearby characters relative to the player, distinguishing between hostile creatures and allies.

At any time, the player can swap their held weapon for another in their inventory; this includes gauntleted fists for delivering melee attacks, which do increased damage when running.

The game's story is presented to the player through computer terminals throughout the single-player levels; their textual content is often accompanied by annotated maps or other still images.

The Marathon games have five difficulty settings: Kindergarten, Easy, Normal, Major Damage, and Total Carnage.

These wall-mounted computer interfaces allow the player to not only learn their mission objectives and aspects of the level map but also to become acquainted with the characters in the story.

Set in 2794, the first Marathon game places the player as a security officer aboard an enormous human starship called the U.E.S.C.

Marathon 2 added elements to the series such as a Lh'owon-native species known as F'lickta, the mention of an ancient and mysterious race of advanced aliens called the Jjaro, and a clan of S'pht that avoided enslavement by the Pfhor: the S'pht'Kr.

Significant additions to the game's world include the Jjaro ship, non-linear level progression, a high-speed flechette gun that could be used underwater, and vacuum-suited human allies carrying fusion weapons.

Both stories take place aboard colony ships orbiting Tau Ceti, where sentient computers have engaged crew and colonists in a fight for survival.

Rampancy is a spontaneous burst in the growth of an AI in a computer network, with an accompanying advance in self-awareness and sudden shifts in personality.

This is a difficult task considering that in order for a rampant AI to survive to this point, it must already be inhabiting a planet-wide or equally complex network.

[4] The three chapters of Marathon Infinity are entitled "Despair", "Rage", and "Envy", suggesting that the player character himself (strongly implied to be a cyborg) may be undergoing his own rampancy throughout the course of the game's events.

As was common for games of that era, 2D sprites are used to portray enemies and NPCs in the level as well as weapons and objects such as ammunition pickups.

Notable new features in the engine included liquids in which the player could swim, ambient sounds, and scripted teleportation of NPCs and items.

It introduced several new types of competitive multiplayer modes beyond deathmatch, such as King of the Hill, as well as co-op play of the main campaign.

It was released in 1996 for the Macintosh only, running on a slightly modified Marathon 2 engine which added support for branching campaigns and fully separate physics models in each level.

Infinity additionally came with "Forge" and "Anvil", polished versions of the internal developer tools used by Bungie and Double Aught to create the series' levels and physics, and to import the game's sounds and graphics.

Since Marathon 2 and Infinity had a settings screen allowing a user-friendly selection of mods (in the form of alternate maps, sprites, sounds, and physics models), this greatly spurred the creation of new fan-made content.

Within the next few years, Marathon 2's engine was officially licensed by other developers to create the games ZPC, Prime Target and Damage Incorporated.

The boxed set was also notable for removing copy protection from the games and including a license allowing them to be installed on as many computers at a site as desired.

[16][17] Aleph One has also been ported to a variety of platforms including Windows and Linux, bringing the Marathon works far beyond their Macintosh roots.

[32] With Bungie's blessing, the team developing the Aleph One engine released the open-sourced Marathon trilogy on Steam for free from May to August 2024.

[36] After Marathon was released in 1994, players began to create mods in the form of custom maps, shapes, sounds, and physics files.

[37] "Vulcan" was a map editor used in the creation of all three games, but it was not released to the public until Marathon Infinity was published, by which time it had been polished and renamed "Forge".

Both Anvil and Forge ran only in the Classic Mac OS, but newer tools have been created by the community for modern platforms.

[43] An original scenario mixing sci-fi and medieval themes, it builds a single-player campaign using new textures and sound assets as well as musical scores.