Zac Vawter climbed the steps in Chicago’s tallest building. (Brian Jackson/CHICAGO SUN-TIMES VIA ASSOCIATED PRESS)

Zac Vawter climbed 2,100 stairs to the top of the Willis Tower in Chicago, Illinois, on Sunday.

That probably seems newsworthy enough. But Vawter, 31, did it with an artificial leg that he controlled with his mind. Pretty cool!

Vawter lost his right leg in an accident and got a replacement that is powered by two motors and his mind. The leg is designed to respond to electrical impulses from muscles in Vawter’s upper leg. When he thinks about climbing, the motors and chains in his leg make his ankle and knee move.

Bionic — or thought-controlled — artificial arms have been available for a few years. But scientists at the Rehabilitation Institute of Chicago have been focusing on legs lately. The reason is simple: If a bionic hand fails, a person drops a glass of water; if a bionic leg fails, a person falls down stairs.

“Everything went great,” said Vawter at the end of the “SkyRise Chicago” event, in which 3,000 people climbed the steps of the city’s tallest building to raise money for research. “The [artificial] leg did its part, and I did my part.”