It's pretty loosely "two sides". It was selected after the SAD, CARS, SET, and BATS crosses were made, so it's not super coherent.
Becky J 🤓8:29 · 2021-12-01T06:56:27.323Z
This was super neat!
Charles Montpetit 🤓1:43 · 2021-12-01T20:37:48.689Z
As I was solving, I thought “This guy really doesn’t abide by the ‘no dupes’ rule”… and then I realized that this was precisely the point. Cute, but in 29a, you can't really clue SAD as an "emotion", as opposed to sadness (try "Tear drop emoji", maybe?). Also, pity that 72d’s ENS is clued as “? ??” in AcrossLite!