Halo: Combat Evolved

Halo: Combat Evolved is a first-person shooter game in which players primarily experience gameplay in a 3D environment from a first-person view. The player can move around and look up, down, left, or right. The game features vehicles ranging from armored tanks to alien hovercraft, many of which can be controlled by the player. The game switches to a third-person perspective during vehicle use for pilots and mounted gun operators; passengers maintain a first-person view. The game's heads-up display includes a "motion tracker" that registers moving allies, moving or firing enemies, and vehicles in a certain radius of the player.

The player character is equipped with an energy shield that nullifies damage from weapons fire and forceful impacts. The shield's charge appears as a blue bar in the corner of the game's heads-up display, and it automatically recharges if no damage is sustained for a brief period. When the shield is fully depleted, the player becomes highly vulnerable, and further damage reduces the hit points of their health meter. When this health meter reaches zero, the character dies and the game reloads from a saved checkpoint. Health can be replenished through the collection of health packs scattered around the game's levels.

Halo: Combat Evolved takes place in a 26th-century science fiction setting. Faster-than-light travel called slip-space allows the human race to colonize planets other than Earth. The planet Reach serves as an interstellar hub of scientific and military activity. The UNSC develops a secret program to create augmented supersoldiers known as Spartans.

More than twenty years before the beginning of the game, a technologically advanced collective of alien races called the Covenant begins a religious war against humanity, declaring them an affront to their gods. Humanity's military experiences a series of crushing defeats; although the Spartans are effective against the Covenant, they are too few in number to turn the tide. In 2552, Covenant forces attack Reach and destroy the colony. The starship Pillar of Autumn escapes the planet with the Spartan Master Chief Petty Officer John-117 on board.

Halo was conceived as an indirect successor to Bungie's previous first-person shooter games, Marathon and Marathon 2: Durandal. After the 1995 release of Durandal, Bungie considered ideas for their next game and wanted to try something other than a direct sequel. One of the ideas that the team began to develop was that of a first-person shooter game described by co-founder Jason Jones as "the natural extension of Marathon, which would have turned out to be something along the lines of Quake". Concurrently, the team explored the concept of a vehicular combat game that featured tank battles in a futuristic setting, internally dubbed "The Giant Bloody War Game".

Jones started the design of a 3D engine that could generate height-mapped graphics to visualize elevated surfaces, and he eventually suggested that Bungie use the technology to realize the "tank combat" idea. The team was enthusiastic about that prospect and proceeded to cancel their first-person shooter project in order to commit to the creation of "The Giant Bloody War Game". However, Jones struggled to implement a physics model to simulate vehicles in the game, which led Bungie to change their plans and develop the real-time strategy game (RTS) Myth: The Fallen Lords, released in 1997.

Halo received widespread critical acclaim, with a 97 out of 100 on review aggregator Metacritic, based on reviews from 68 professional critics. Ste Curran's review for Edge praised the game as "the most important launch game for any console, ever" and commented, "GoldenEye was the standard for multiplayer console combat. It has been surpassed."

GameSpot claimed that "Halo's single-player game is worth picking up an Xbox for alone", concluding, "Not only is this easily the best of the Xbox launch games, but it's easily one of the best shooters ever, on any platform." IGN remarked similarly, calling Halo a "can't miss, no-brainer, sure thing, five star, triple A game". Gary Whitta of Official Xbox Magazine called Halo "a stunning achievement". AllGame editor Jonathan Licata praised Bungie for doing "a remarkable job with Halo, taking many successful elements from previous standouts in the genre to make one very playable game". Among the specific aspects that reviewers praised were the balance of weapons, the role of drivable vehicles, and the artificial intelligence of enemies.

Halo is credited with modernizing the FPS genre. According to GameSpot, Halo's "numerous subtle innovations have been borrowed by countless other games since". The game is often cited as the main reason for the Xbox's success, and it began what is commonly regarded as the system's flagship franchise. biz published an article estimating Halo as the second-highest revenue-generating 21st century console video game in the United States, behind Grand Theft Auto: Vice City.

The game's popularity sparked the usage of terms such as "Halo clone" and "Halo killer", applied to games either similar to or anticipated to be better than it. The Halo engine was used for the game Stubbs the Zombie in Rebel Without a Pulse.