Answer the following Q with stream of consciousness. Context: The characters Connor and Markus are played by Bryan Dechart and Jesse Williams, respectively. Clancy Brown, Lance Henriksen, and Minka Kelly portray supporting characters Lieutenant Hank Anderson, Carl Manfred, and North, respectively. There are three different composers, one for each playable character: Philip Sheppard for Kara, Nima Fakhrara for Connor, and John Paesano for Markus. Sheppard's cello sequence in Kara's theme was inspired by the flames of a log fire, whereas the motif layered over it came from the two syllables in her name. Fakhrara created custom instruments and used vintage synthesizers in order that the sound could represent the robotic nature of Connor. Paesano's music was made with the idea that it would be "like a church hymn", personifying Markus' transformation into a leader. Sheppard recorded at Abbey Road Studios with the English Session Orchestra; Paesano was at Synchron Stage Vienna with the Synchron Stage Orchestra. Director of photography Aymeric Montouchet used "thick grain and shaky long lens" with shallow depth of field for Kara, "small, tight grain" and a blue palette for Connor, and orange and white colours for Markus. The game was released to manufacturing on 23 April 2018, after four years of production.

Question: how long was detroit become human in development for?
The relevant sentence in the passage is: The game was released to manufacturing on 23 April 2018, after four years of production. Therefore, the final answer is four years.