Leo tried them on. They felt sturdy, but heavy—like he was wearing bricks designed by NASA. He moved to the next pair: sleek, white, and impossibly light.

The clerk, a teenager named Toby who moved with the grace of someone who actually practiced his footwork, dropped three boxes on the bench.

"The speed demons," Toby chirped. "Minimalist. You’ll feel every pebble, but you’ll fly."