LAS VEGAS — The clatter of 200 Rubik’s Cubes twisting in unison filled the ballroom at the Riviera hotel and casino here on Saturday as Riley Woo, 15, stepped to the stage.

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He took 1 minute 46 seconds to study a jumbled cube, then pulled a blindfold over his eyes and started to twist.

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Forty-eight seconds later, Riley lifted his blindfold and smiled. He had solved the puzzle, in a total of just over 2 minutes 34 seconds; not bad. Across the table, his father stopped filming and give him a thumbs-up.

“I just memorized each color, and then based on that, like, you already know how to solve it, based on where each color is,” Riley said afterward.