Occasionally I turn around to see him reaching for Rosty's chair. Or Jet sees me looking and lights up and burst out laughing and celebrating the attention. It's not that he needs the attention, he's doing fine without it, playing away full-bore; but he seems to really enjoy it when Rosty or I turn around to talk with him for a while.
This is pretty cool. I can just close the office door and it becomes an effective play pen, with piano, toys, and lots of room for roaming. He's getting really mobile, though he still doesn't go forward. It's still rolling sideways and crab crawling backwards, but he seems quite content to go where he wants. I'm pretty amazed by how well he gets around, even though there's a lot of obvious effort that has to go into it. He really seems to be enjoying the challenge and pushes, claws, and grunts with effort at every move, but I guess he's wired to learn that way.