Professor Yoo Aryeon, the Stickler

Once she got past the first hurdle, everything after that went astonishingly smoothly.

It was like twisting open a completely clogged faucet and watching water gush out—whoosh, whoosh, whoosh!

Once Mom confirmed there were only finitely many walls, she began smashing through them one by one.

Each time she crossed a wall, she calculated how many strata had their stability conditions reversed.

Then she checked, one by one, that those changes could be expressed using lower values of c₂.

Scratch-scratch-.

Flip-.

Scratch-scratch-scratch-.

Mom's notebook grew thicker by the day all over again.

Every morning, I took the notebook and read it, and in the afternoon, Mom came back with answers to my questions...