The original idea that sparked this puzzle was "a day at the airport," where each common phrase began with an action you'd take when traveling by air: Drive, Stand (TSA line), Run ("I'm never gonna make it!"), Sit ("Whew!"), Fly. I never made that grid and really don’t remember why I changed the theme to what you see today, which became "The Evolution of Human Transport." The only road bump along the way was at 31-Down, whose entry was originally IMBEDDED IN, a very rare variant of EMBEDDED IN; not being able to come up with an alternative, I thought about changing the theme entry to DRIVE UP THE VALUE, which sounded a bit off. Back to the drawing board, and trial and error gave me IS WEDDED TO. Not being too sure of that one either, I sent David the first version, and when he balked, the second. He accepted it.
This puzzle is a perfect example of what I like for the early week! The theme itself is simple, yet it's elevated by the progression from WALK to ROCKET. Also, all four theme entries are lively and in-the-language—my favorite is ROCKET TO STARDOM, which I believe is making its crossword debut. Working around 60 theme squares is always tough, though Jules rose to the challenge and even squeezed in a pair of long downs. I was worried he'd have to scrap said long downs to get rid of IMBEDDED IN, though his IS WEDDED TO suggestion saved the day. Your thoughts?