In the game, the player controls "the Kid" as he moves through floating, fantasy-themed environments and fights enemies of various types.

It features a dynamic voiceover from a narrator (Logan Cunningham), and is presented as a two-dimensional game with an isometric camera and a hand-painted, colorful art style.

The game was built over the course of two years by a team of seven people split between San Jose and New York City.

[1] There are a limited number of special attacks that the player can perform at any time, represented by "black tonics" that can be found in the levels or dropped from enemies.

This narration gives scripted plot information as well as dynamic comments, such as on the player's skill with a weapon or performance while fighting enemies.

[4] Between levels, the Kid visits the Bastion, where the player can use fragments—the game's form of currency—that they have accrued to buy materials and upgrade weapons.

[5] Experience points are used to determine the Kid's ability level; higher values give the player more health and increase the number of upgrades they can select.

The challenges differ depending on the weapon, such as destroying a certain number of objects within a given time or breaking targets in the fewest shots possible.

Players take control of the Kid, a silent protagonist who awakens on one of the few remaining pieces of the old world and sets off for the eponymous Bastion, where everyone was supposed to go in troubled times.

[8] The only survivor he meets there is an elderly man named Rucks, the game's narrator, who instructs him to collect the Cores that once powered Caelondia.

A device in the Bastion can use the power of the crystalline Cores to create landmasses and structures, as well as enable the Kid to travel farther afield via "skyways" that propel him through the air.

He had helped Caelondian scientists ("Mancers") build a weapon intended to destroy the Ura completely to prevent another war.

After the Kid returns and recovers, Rucks gives him another choice: He can have the Bastion rewind time to before the Calamity in the hopes of preventing it, or use it to evacuate the survivors and move on to somewhere safe.

[20] The game ends either way, showing images of the characters (with the inclusion of Zulf if the player chose to rescue him) flying away or of their lives before the Calamity along with the credits.

The co-founders of Supergiant Games, Rao and Simon, previously worked for Electronic Arts, where they helped develop Command & Conquer 3 and Red Alert 3.

[24] Most of the team built the game in a house in San Jose, though the music and voice acting were recorded in New York City.

[25] The team chose the design elements of a fractured, floating world due to their wish to portray a sky in the game, which is usually not possible with an isometric camera, as it always points down.

The hand-painted style was intended to soften the sharpness she saw as typical in isometric games and the colorless, harsh depictions of most devastated landscapes.

[25] The narrator was added early in the game's development as a way to provide background details and depth to the world without requiring the player to read long strings of text or wait through cutscenes.

[29] Bastion was released on July 20, 2011 for Xbox Live Arcade (XBLA), and on August 16, 2011 for digital distribution on Windows through Steam.

[26] Bastion was the first video game that Korb had scored; prior to it he had worked on a few smaller television shows and movies.

[39] He was brought onto the team in the beginning stages of the project, and several of the pieces he developed were created prior to the final design of the levels with which they were associated.

[39] The music was recorded in Korb's closet at his New York City apartment, as were the sound effects and more than three thousand lines of narration by Cunningham.

The soundtrack features four vocal themes: "Build That Wall", "What's Left Undone", "Mother, I'm Here", and "Setting Sail, Coming Home".

[28] On March 15, 2012, Supergiant Games released sheet music for piano and guitar arrangements by Korb of "Build That Wall", "Mother, I'm Here", "Setting Sail, Coming Home", and "The Pantheon (Ain't Gonna Catch You)" free in their online store.

[58] Bob Mackey of 1UP.com called it "the perfect mesh of game and story", and McKinley Noble of GamePro said that it "raises the visual and narrative bar for downloadable titles".

[49] Edge said that the narration added "emotional resonance" to the game, and Tom Bramwell of Eurogamer praised the "dazzling visuals" and "artful commentary".

[1][49] Edge said that the gameplay was "more interested in variety than challenge", for which he praised it, and Matt Miller said that combat was "a lot of fun", though he felt it lacked "the depth, speed, or complexity of a true action game".

[4][50] Greg Miller highlighted the variety of the gameplay as the best part of the game, and Scott called it "enjoyable", though not "challenging".