Boulder is waiting for his playmate to grow up

Our adult cat, Boulder, cannot wait for Temba to get big enough to play with him. Yesterday, he tried to play peek-a-boo on the stairs. Temba was wandering around on the top floor (under my close eye, of course) and Boulder got on the steps. He poked his head out and batted his paws on the top of the stairs until Temba looked at him. Then, he ducked his head behind the stair to hide himself. Eventually, he would poke his head back up and do it again. Temba doesn't quite understand it yet, but I am sure it will be a fun game for the two of them in a week or so.