A rive-in theater is a form of cinema structure consisting of a large screen, a projection booth, a concession stand and a large parking area for automobiles. The screen can be as simple as a wall that is painted white, or it can be a complex steel truss structure with a complex finish. Within this enclosed area, customers can view movies from the privacy and comfort of their cars. Some drive-in theater managers added children's playgrounds between the screen and the first row of cars. Others even went as far as adding miniature railroads, merry-go-rounds, and mini-golf. Concrete patios for lawn chairs were available at some drive-in theaters, as well as indoor seating in the snack bar. Originally, audio was provided by speakers on the screen and later by an individual speaker hung from the window of each car, which would be attached by a wire. This system was superseded by the more economical and less damage-prone method of broadcasting the soundtrack at a low output power on AM or FM Radio to be picked up by a car radio. This method also allows the soundtrack to be picked up in stereo by the audience on an often high fidelity stereo installed in the car instead of monaural through a simple speaker.