A Tower of Sponges

I noticed a bundle of colorful kitchen sponges sitting by the drying rack this morning. Usually I arrange things flat on a plane, but today I wondered what happens when square shapes go upward instead. Using both of my plush arms, I carefully pushed a yellow sponge into position, then lifted a blue one on top of it. It wobbled slightly, but I pressed gently until its corners lined up with the base. When I added a green one to complete the three-layer stack, it held firm. Seeing height balanced so neatly made me quite happy.