I never thought a bunch of numbers in little boxes could keep me awake past midnight — but here we are. Me, hunched over my phone, eyes squinting at a 9x9 grid, whispering like a mad scientist, “If this 6 goes here, then the 3 must go there…” Some people unwind by watching TV or scrolling through memes. I, apparently, prefer battling an invisible enemy made of logic and...