The themes of self-forgiveness present in the narrative began with the idea of creating a "more introspective" game, and later grew to become intertwined with the gameplay.

On September 9, 2019, a free downloadable content (DLC) expansion named Farewell was released, introducing a new chapter to the game.

[3][7] Chapters contain branching paths leading to optional challenges and hidden collectibles, including strawberries, cassette tapes,[7][3] and crystal hearts that unlock certain gates.

After ignoring Granny, Madeline encounters an abandoned city, where she meets Theo,[19] a social media-obsessed traveler from Seattle.

After finally reaching the summit, a heartfelt scene plays where the two enjoy a strawberry pie with Granny, Theo, and Oshiro.

[c] Due to self-imposed restrictions and time limitations, Thorson and Berry wanted the game to be minimal with additional mechanics to add complexity, to which they felt the idea of a character struggling to climb a mountain was fitting.

[33] Thorson and Berry cited multiple games as having influenced the gameplay of Celeste, including Donkey Kong Country 2 (1995), Metroid (1986), and Kero Blaster (2014).

[41][29] Additional mechanics include the ability to buffer the input for a jump before touching the ground, a mechanic that simulates rounded corners to prevent the player from colliding with a corner,[42] and one that allows players to jump off of a wall while slightly in front of it rather than requiring direct contact.

[47] The implementation of an accessibility option was decided on after observing public discourse surrounding Cuphead (2017) that originated after many players felt that the game was too difficult or unforgiving.

[49] The themes of Celeste took inspiration from Studio Ghibli films such as Spirited Away (2001),[50] and the developers knew that they wanted it to be more introspective compared to the more extroverted nature of TowerFall.

This transformed Celeste into a game about remembering to take care of oneself, and recognizing that sometimes self-improvement is necessary to avoid hurting others.

Thorson recalled that she initially knew she wanted Madeline to fall down the mountain and later finish climbing, but she did not know how to execute or frame it in the story as a whole.

She decided to make it clear to the player that reaching the summit was not the end of Madeline's story, and that her depression and anxiety were not "magically better".

Its synthesizer-heavy sequences, noted by Raine to be reminiscent of Vangelis and Blade Runner (1982), were designed to match the "cosmic horrors" experienced by Madeline.

[16][61] Initially planned to be a self-contained collection of extremely difficult levels,[62] the expansion later grew in scope to include a new narrative continuing from the story of the base game.

Prescriptions for Sleep: Celeste features violin by Maiko, saxophone by Norihiko Hibino, and piano by AYAKI, with Raine serving as co-producer.

[74] An open pre-order window for a Celeste collector's edition produced by Limited Run Games began on January 1, 2019.

[80][81] The final chapter of Celeste, Farewell, was released as free DLC on September 9, 2019,[82][83] however the team noted that the Xbox One version would have a slight delay.

[3] It was considered by Hardcore Gamer to be among the best games of 2018,[3] and Ars Technica called it "the most intense, memorable, and satisfying platformer" of the 2010s.

[6] The variety and implementation of the game mechanics were praised,[9] despite PC Gamer lamenting the addition of strong winds as a "huge momentum killer".

[i] Nintendo Life praised its implementation, customizability, and unintrusiveness,[8] and Hardcore Gamer found that it was an "innovative way to make the game truly accessible to everyone".

[j] Polygon described Theo as a "lighthearted, constant foil" to Badeline,[6] and the dialogue overall was praised, with Hardcore Gamer saying that it helped to "flesh out" the characters,[3] and VideoGamer.com appreciated how it further contributed to the narrative being relatable.

[20] The story was considered by critics to be "heartfelt", "touching", or "heartwarming",[k] and some felt that it was a 'timely' narrative,[92][7] meanwhile others found it to be occasionally inspirational.

[95] Reviewers felt that it remained enjoyable to listen to even after extended periods of time,[5][23] and certain aspects of the music were praised, such as the synthesizer or piano portions.

[6][8] Critics also appreciated the remixes of songs present in the B-side levels,[92] with Nintendo World Report saying they were "just as magnificent" as the rest of the music.

[15] However, USgamer noted that they were unable to complete the chapter due to its difficulty, adding that the base game's B-side and C-side levels similarly caused them to "hit a wall".

Mechanics are adjusted to accommodate players who wish to perform advanced techniques, though it is often done subtly to preserve the feeling of "breaking" the game.

[48] Upon release, Celeste received several nominations and accolades, including for Game of the Year, from outlets and award shows.

[102] Prior to release, Berry commented that a potential sequel to Celeste was not currently planned, saying that the team "told the story [they] wanted to tell".

The sequel stars a new character, Lani, who makes use of a grappling hook to interact with objects and climb Celeste Mountain.