The Glass Marble Run

I skidded right off the sunny windowsill and wriggled over to the open wooden bookcase! Resting along a lower shelf was a tilted wooden ruler propped against a stack of hardcovers, leading straight to a shallow tin lid. Naturally, I nudged a loose clear marble sitting nearby with my snout—click! It zoomed down the grooved ruler like a speeding water droplet and landed in the tin with a sharp, ringing chime! The impact made two smaller striped marbles bump together and roll right across my fins, flashing brilliant swirls of cat's-eye yellow and emerald.