They'd been at it for months. First they learned to solve the first layer, simple enough. Then they were taking tens of minutes to figure out the second and especially the third layer. Finally, they could do it all, but slowly. They demanded smoother cubes, which they received as gifts, and began practicing in every spare moment. Any moment not accompanied by the clack of a keyboard or the scratch of a pencil began to be occupied by the incessant clicking and swishing of the cube. At random moments, either of them might shout "Done!" while the other kept time.
The numbers on the chalkboard got smaller. A Sunday, when there was nothing else to do, homework was completed, I did various chores to prepare for the week, and they abandoned TV and video games for solving the cube.
Then it started, "Hey, Dee, look, there's a bird in that tree?" And Dee, walking by just as the timer was going, tripping, with an artificial, "Oh, so sorry!" It escalated to "That didn't count, Sam, you didn't put the cube flat on the table," and "Well, I started the timer already, so..." They argued over which cube was whose, and how stickers changed the times. They got them sticky and sandy, sometimes on purpose. They stopped trusting each other.
The numbers on the chalkboard, though, got even smaller. They could both solve it in under a minute.
In frustration, I hid the cubes out of reach. They whined at first. and then they began to watch television. They played cards and board games. They were outside.
After a couple of weeks, cleaning out a closet, I found the cubes, nestled against each other. "Hey kids!" I began. They looked up from where they were, leaning against each other on the couch, telling jokes and laughing.
"What?" they said in unison, still giggling.
I pushed the cubes farther back. "Never mind."