Two dance troupes rehearsed in opposite corners of the studio — the red company in the upper left, the blue company in the lower right. Each day they drifted closer to center, learning each other's choreography. On the fourth day the director made the call: the red company would take the blue company's stage position, and vice versa. They crossed over completely, red settling into the lower-right corner, blue claiming the upper left. On the fifth day they were already rehearsing in their new homes, indistinguishable from the originals except for the color of their costumes.