Coasting on sheer joy, this genial, feel-good family drama reveals what a perfect pairing of subject and medium roller skating and movies can be – it’s a celebration of movement in an art form defined by movement. Tracing the coming of age of a roller-rink teen (a sweetly gawky Bow Wow) and his buddies in 1978 Chicago, director Malcolm D. Lee throws some wheels on his cameras, hits the floor with his ebullient stars and suddenly we’re right there too, swerving in and out, with Earth Wind & Fire in our ears and visions of disco balls dancing in our heads.