Art car recent years the festival has been forced to limit the number of vehicles on the playa. As such they have restricted the vehicles that are licensed to what they are now calling "mutant vehicles". There has been some confusion within the Burning Man and Art Car communities over these two terms, with some believing the terms are simply synonyms. According to art car artist and Art Car Fest organizer Philo Northrup, art cars are "street-legal vehicles that have been permanently transformed into mobile sculptures". According to the Burning Man DMV ("Department of Mutant Vehicles"), Mutant Vehicles are "'art on wheels':
Mathematics and art Optical illusions such as the Fraser spiral strikingly demonstrate limitations in human visual perception, creating what the art historian Ernst Gombrich called a "baffling trick." The black and white ropes that appear to form spirals are in fact concentric circles. The mid-twentieth century Op art or optical art style of painting and graphics exploited such effects to create the impression of movement and flashing or vibrating patterns seen in the work of artists such as Bridget Riley, Spyros Horemis, and Victor Vasarely. A strand of art from Ancient Greece onwards sees God as the geometer of the world, and the