Who doesn’t love the circus—especially nouveau cirque? With its unclassifiable blend of genres, it reflects so much of what it means to be human—the comedy, absurdity, beauty, sadness, delight, and more. Always tinged with physical risk or challenge, circus inspires childlike wonder. So when I noticed PS21’s dedicated programming of cirque offerings this season, I made the trip upstate to the Hudson Valley to this progressive contemporary arts venue on a bucolic, 100-acre campus. The venue, with its open-air Pavilion theater, was the ideal setting for the US premiere of “Runners,” by Cirk la Putyka from the Czech Republic.