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 plastic canvas instead. Their "mathghans" (Afghans for Schools) project introduced knitting into the British mathematics and technology curriculum. Modelling is far from the only possible way to illustrate mathematical concepts. Giotto's "Stefaneschi Triptych", 1320, illustrates recursion in the form of "mise en abyme"; the central panel of the triptych contains, lower left, the kneeling figure of Cardinal Stefaneschi, holding up the triptych as an offering. Giorgio Chirico's metaphysical paintings such as his 1917 "Great Metaphysical Interior" explore the question of levels of representation in art by depicting paintings within his paintings. Art can exemplify logical paradoxes, as in some paintings