Through Parker and Delamater’s remarkably empathetic performances, any one version of the couple comes to feel like the sum of its multiplicity. And its exquisite final moments, Constellations lets Marianne and Roland waltz in the vastness of their possibilities. As Marianne and Roland dance, their infinite choices — and the limits of knowing only one at a time — scintillate in the air. We might feel our own myriad selves hovering somewhere close.