(warning, nerd alert) Ah, a math puzzle! Even better, a geometry puzzle! It's a shame that this didn't run on Pi Day (3/14), but a person can only dream. Jean uses the famous formula for area of a circle, pi*r^2 (or "PI R SQUARED"), and for circumference, 2*pi*r, where r is the circle's radius. It took me a while to figure out what was going on with 2 PI R because I always think of it as PI D (d = diameter), but sure enough, 2 PI R is totally legit.
And to top it off, Jean's incorporated FULL / CIRCLE into the grid, a nice revealer hinting at the two formulas. I like that it doesn't hit you over the head like some revealers do; rather, it hints at what's going on, leaving the rest up to the solver's imagination. I would have liked to seen FULL / CIRCLE not split up, or at least placed in closer proximity, since I don't like jumping all over the grid for cross-referenced clues. Placing those answers both in the SE corner would have achieved that, plus would have given the added bonus of not having the revealer appear until the solver is near the end of the puzzle. But that might have been quite difficult to achieve, given the grid layout.
Rebus squares can be tricky, and typically I like to see them kept to four letters squished in or less. SQUARED obviously can be much better represented by a superscript "2" in print, but plenty of solvers will prefer to write in SQUARED since SQUARED AWAY looks so much more correct than ^{2} AWAY. I did like the variety of it all, in that experienced solvers aren't used to having a mix of rebus squares, regular ones, and numbers. Neat mix.
Because the theme is squeezed into compacted areas, the rest of the grid is fairly wide open. Jean does a nice job of incorporating other long fill, such as BIKINI TOP (my favorite, of course), BANISTER with its neat misdirectional clue (flight of stairs, not airplane flight), and TAX EVADER with a great clue, "duties" meaning "levies," not "responsibilities." Great to get a healthy dose of wordplay. There are some compromises like OR IN, ORO, WE SAY, but I sure liked getting all the great long stuff. Not a bad trade-off.
Finally, for those of you wondering, FOURH is good old 4-H. It's strange to me since I never see 4-H written FOUR-H, but it's almost kooky-looking enough for me to I like it.