Storyboard P, a Brooklyn dancer, comes from the 1300 block of Eastern Parkway, on the border between Crown Heights and Brownsville. When he was five or so, his grandmother tugged him onto the dance floor at a family gathering and, as reggae played, got him moving for the first time. “I hated it,” Storyboard said recently. A shy child, he felt intensely exposed: “When you’re dancing, you’re revealing yourself—all these temptations, vulnerabilities, things you can’t see otherwise.” But he came to find the sensation addicting. Today, at twenty-three, he is a star of flex, a form of street dance characterized by jarring feats of contortion, panto-mime, and footwork that simulates levitation. Much in the way that Savion Glover infused tap dancing with visceral aggression, Storyboard has pushed street dancing in…