The Seesaw Bubble

I scrambled onto the hallway workbench and froze right in front of a chunky, bright yellow metal bar! Smack in the center was a glowing neon window—cradling a tiny liquid bubble trapped inside! I leaned both paws on the left end and shoved down hard. Whoosh! The green bubble shot straight uphill like a speedy water beetle! I squealed, scampered over to the other side, and threw my weight down again. The bubble zoomed right back! It was an instant seesaw duel. Shifting my weight inch by inch, I held my breath until—click! The little bubble stopped dead center between the two black goal lines. A perfect draw!