A wild mouse is a type of roller coaster consisting of single or spinning cars traversing a tight-winding track with an emphasis on sharp, unbanked turns. The upper portion of the track usually features multiple 180-degree turns, known as flat turns, that produce high lateral G-forces even at modest speeds. Cars are often designed to be wider than the track to enhance the illusion of hanging over the edge. Lower portions of the track typically feature small hills and bunny hops. Wild mouse coasters first appeared in the 1950s, and following a period of decline in the 1980s, new innovations and layout designs in the late 1990s led to a resurgence in demand.