Tin would eventually be hired to work on Johnson's game Civilization IV, where he composed the Grammy winning song Baba Yetu.
Johnson followed the Civilization III development externally and jumped at the chance to join his idol Sid Meier.
Johnson joined Firaxis in April 2000 and, along with Jake Solomon, started mid-development on Civilization III with director Sid Meier and designer Jeff Briggs.
Johnson simplified Civilization III's code base so that a lot of new mechanics could be added, without having to simply keep building on top of the previous game.
Johnson's hardcore resource features in Civilization III created scarcity in economic terms, becoming a catalyst for diplomacy system.
Johnson provided updates and patches to Civilization III for a year after the initial release, spending plenty of time immersed in the game's community, judging and absorbing feedback.
Johnson also had a considerable role in the development of the main theme music: Baba Yetu, by working with his old classmate and composer, Christopher Tin.
Christopher and Johnson, wanted to capture the essence of the view of Earth from outer space in a musical piece, but also giving a deeper feel to the song with an extra layer of lyrical meaning.
Some fans of Civilization IV reportedly ended up leaving the menu screen open just to hear the global beat on repeat.
On April 17, 2007, it was announced that Johnson had left Firaxis to rejoin Electronic Arts (Maxis) to start mid-development on the genre bending game based on evolution, Spore.
The game simulated 5 phases of evolution, starting the player as single cell and ending as an intergalactic civilization.
At EA, Johnson also worked on the design of Dragon Age Legends, a Flash game released for Facebook and Google+ in March 2011.
Johnson left EA in September 2011 to join the social network game development company Zynga on an unnamed project that was never published.
Offworld Trading Company would end up being a commercial success, selling over 600,000 copies, and achieved a broadly positive critical reception.
After the development of Offworld Trading Company, Mohawk started work on a new historical based Civilization-inspired strategy game initially called 10 Crowns.