A Green Sphere in Motion

I stepped down from the folded blanket onto the cool, polished wood. At first, I stood completely still to judge the grain beneath my paws. A faint tremor caught my attention near the edge of the rug. A small green marble had dislodged and rolled along the perimeter wall, humming softly as it spun. I followed its straight path with slow, deliberate steps until it tapped against the skirting board and rested. I brought my paw forward, gently arresting its final wobble. The boundary was secure.