Pyta acted as the primary developer for most of the game's six-year production, having to rely upon personal intuition to design the pacing due to playtesting difficulties.

After the king falls asleep to regain his diminished powers, the Shade is tasked with awakening its master after 400 days in real time.

[1][2][3] The Shade can explore caves, gather resources to furnish its home, or perform other activities such as reading classical literature and drawing.

[7] Another mechanism called the "bookmark system" can be accessed through a menu, and the player can use it to instruct the Shade to automatically walk to a previously saved location, return to its home, or randomly wander around.

[7][9] The player is provided a to-do list of things to improve the Shade's life,[10] but no interaction is required to advance the timer, and it continues even if the game is not open.

Alternatively, if the Shade explores enough of the caves close to the surface world, it discovers a dark cavern at the edge of a bottomless pit.

Depending on how the player previously interacted with the Shade, it will either hide itself from the Darkness by closing its eyes, or be caught by the creature and sent back to its home.

[4][12] Developer Anselm Pyta had a background creating flash animations that were released on Newgrounds, until he co-founded Studio Seufz in 2017.

[4] Pyta was especially interested in exploring time-based and waiting mechanics, believing that video games are the only medium that could uniquely use extended time to tell a story.

[4][5] Pyta defined The Longing's theme of loneliness while he was studying, and the lonely and subterranean atmosphere was inspired by dungeon synth music.

[14] He imagined three possible routes that the player could take: waiting idly for the timer to advance, trying to make the Shade's life comfortable during the 400 days, or abandoning the king and leaving the caves.

Waiting offered a stress-free way of playing the game; leaving forced the player to solve puzzles and navigate increasingly dangerous caves.

[4][5] To show players that progress was being made, he implemented behaviors for the Shade that changed as time passed, such as self-talking and sleeping.

[15] The Longing was published by Application Systems Heidelberg[1][2] and released on March 5, 2020, to Steam for Windows, macOS, and Linux,[16][17] followed by a version for Nintendo Switch on April 14, 2021.

The Washington Post praised the slowness for allowing the player's mind to wander, comparing it to the works of filmmaker Béla Tarr.

[2] Similarly, Hardcore Gamer said that the appeal of the Shade helped pass the time, and eased the player into the pacing naturally.

[9][30] In a more critical review, Nintendo Life commended the art and sounds for their boldness, but found the atmosphere to be dull and uninteresting.

[3][28] Adventure Gamers appreciated the music for representing a medley of emotions, feeling that the songs expressed the Shade's small size in such a large subterranean kingdom.

[3] Wired wrote that the Shade felt alive in a magical way, and that The Longing best captured "2020's sad and surreal lockdown energy".