[8] As reported in David Kushner's Masters of Doom, when Carmack was 14, he broke into a school with other children to steal Apple II computers.

To gain entry to the building, Carmack concocted a sticky substance of thermite mixed with Vaseline that melted through the windows.

Later, Softdisk would place this team in charge of a new, but short-lived, bi-monthly game subscription product called Gamer's Edge for the IBM PC (DOS) platform.

In 1990, while still at Softdisk, Carmack, Romero, and others created the first of the Commander Keen games, a series that was published by Apogee Software, under the shareware distribution model, from 1991 onwards.

[13] Carmack has pioneered or popularized the use of many techniques in computer graphics, including "adaptive tile refresh" for Commander Keen,[14] ray casting for Hovertank 3D, Catacomb 3-D, and Wolfenstein 3D, binary space partitioning which Doom became the first game to use,[15] surface caching which he invented for Quake, Carmack's Reverse (formally known as z-fail stencil shadows) which he devised for Doom 3, and MegaTexture technology, first used in Enemy Territory: Quake Wars.

[17] Carmack's engines have also been licensed for use in other influential first-person shooters such as Half-Life, Call of Duty and Medal of Honor: Allied Assault.

[23][24][25] The trial jury absolved Carmack of liability, though Oculus and other corporate officers were held liable for trademark, copyright, and contract violations.

Not only does high intensity allow him to make progress more quickly, but long hours are also critical to maintaining a focused mindset over time.

[31] The goal of these retreats is to allow Carmack to operate at full cognitive capacity, tackling a specific, difficult problem or learning a new skill.

[32] The solitude and physical isolation of these retreats offer the perfect environment for deep focus and reflection, making them an essential part of Carmack's creative process.

[33] In his departure memo, he stated, "We have a ridiculous amount of people and resources, but we constantly self-sabotage and squander effort," he wrote.

Reviewing how much money he was spending on customizing Ferraris,[citation needed] he began by giving financial support to a few local amateur engineers.

In October 2008, Armadillo Aerospace competed in a NASA contest known as the Lunar Lander Challenge, winning first place in the Level 1 competition along with $350,000 (~$486,412 in 2023).

[50] Carmack has since advised developers to be careful when utilizing middleware, noting how it can limit the possibilities of later releasing source code.

[51] Tim Sweeney has implied this issue has hindered potential releases of older Unreal Engine source code.

[52] On the other hand, despite his technical admiration for the system,[53] Carmack has several times over the years voiced a sceptical opinion about Linux as a gaming platform.

As a bet, Kang challenged Carmack to sponsor the first all-female Quake tournament if she was able to produce a significant number of participants.

Carmack also reflected on the internal development of Quake in this regard and described it as "traumatic" and says id Software could have split the game into two parts and shipped it earlier.

[67] Carmack has a blog last updated in 2006 (previously a .plan, which could be accessed by making a finger request for johnc@idsoftware.com[68]), an active Twitter account, and also occasionally posts comments to Slashdot.

[71][72] During a conversation with Joe Rogan, Carmack revealed that he had trained in Brazilian Jiu Jitsu and Judo for several years as a hobby.