On 12 January 2009, Ian Bell acquired the business and assets of Blimey! Games from the bankrupt parent company 10tacle Studios, forming Slightly Mad Studios. The new studio's first major release came in September 2009 with Need for Speed: Shift, developed in collaboration with Electronic Arts. The sequel, Shift 2: Unleashed, was announced in November 2010 and released in March 2011. The company operated with a distributed development structure, with team members working remotely from locations around the world — an unusual model at the time. Slightly Mad was ranked 17th in the Develop 100 list of most successful developers for 2010.
In 2012, the studio released Test Drive: Ferrari Racing Legends, a title dedicated to Ferrari's legacy across Formula One, rallying, and sports cars.
In 2015, Slightly Mad Studios launched Project CARS, a racing simulator developed with direct community involvement in funding and pre-alpha testing. This community-based development model was designed to bypass conventional publishing costs. Project CARS was subsequently featured in professional esports competitions organized by ESL from 2015 to 2018.
Project CARS 2 followed in 2017, again using the community-development approach. The title ran on the studio's proprietary Madness engine and expanded on the original's content. In May 2019 it was announced that Automobilista 2, developed by Reiza Studios, would also use the Madness engine, with the game releasing in mid-2020.
In January 2019, CEO Ian Bell announced via social media that Slightly Mad Studios intended to develop its own gaming console, to be called Mad Box. Bell described it as "the most powerful console ever built," with claimed specifications including 4K resolution at up to 120 FPS and support for major VR headsets at 60 FPS per eye. The company planned to offer developers free access to the Madness engine for the platform and did not intend to pursue exclusive titles. The console was projected for a 2022 release, but no further development was publicly demonstrated.
Slightly Mad Studios was acquired by Codemasters in November 2019 for approximately US$30 million. The deal included the rights to the Project CARS series and a then-unannounced game. The studio's third mainline release, Project CARS 3, launched in August 2020 — three weeks after the publisher also released Fast & Furious Crossroads.
Codemasters was itself acquired by Electronic Arts in February 2021, bringing Slightly Mad Studios into the EA portfolio. That same month, a free-to-play mobile title, Project CARS Go, was released by Gamevil. The mobile game was withdrawn from sale in October 2021, with services shut down the following month. Ian Bell departed the studio in October 2021.
Under EA's stewardship, Project CARS and Project CARS 2 were removed from digital storefronts in 2022 as vehicle and circuit licenses expired. On 8 November 2022, EA announced the discontinuation of the entire Project CARS series and the redeployment of Slightly Mad Studios staff to other internal projects. Bell, who had already left the studio, announced a new venture called Straight4 and offered positions to employees affected by the restructuring.
Slightly Mad Studios occupied a distinctive position in the racing-game landscape, bridging the gap between the mass-market Need for Speed franchise and the hardcore simulation audience. The Project CARS series, despite its eventual cancellation, demonstrated that community-funded racing simulators could achieve mainstream commercial release and esports integration. The Madness engine, developed in-house, continued to underpin Automobilista 2 after the studio's closure, extending the technology's lifespan beyond the fate of the Project CARS brand.