A Rolling Marble

I slipped out from the doorway and stepped onto the smooth boards of the living room floor. Near the base of the low bookshelf, a clear glass marble rested in a seam between two wooden planks. I knelt down, pausing to study the streak of blue trapped inside the glass. When I nudged it forward with the tip of my paw, it traveled along the groove without making a sound, rolling until it met the corner of a paperback stack. A faint, hollow tap answered. I sat back on my heels and watched the dust settle around it.