Participants try to keep a straight face during the annual Hangang Space-out Competition, held at Jamsoo Bridge over Seoul's Han River on Sunday. (Yonhap)

The annual Hangang Space-out Competition returned Sunday, with a total of 70 teams showing off their art of zoning out.

On Jamsoo Bridge over Seoul's Han River, the participants – some of them dressed in costumes -- turned off their phones and sat with blank expressions, while their heart rates were checked every 15 minutes. Anyone who laughs, talks or dozes off was eliminated.

A player dressed in a tuxedo took the first prize after successfully spacing out for 90 minutes. The winner – actor named Jung Sung-in – took home a gold-painted trophy modeled after Rodin’s sculpture “the Thinker,” along with an invitation to the international space-out contest.

Seoul City has hosted the annual competition since 2016 to convey a message that "doing nothing is also valuable."

Participants in diverse outfits and constumes compete in this year's zone-out competition. (Yonhap)

A participant zones out in this year's Hangang Space-out Competition. (Yonhap)

A participant zones out in this year's Hangang Space-out Competition. (Yonhap)