The framed row hides two ghosts in five cells: choosing 2 from 5 gives ten ways. One × cuts it to six (2 from 4) — a single × just erased four possible worlds. A deduction is the moment the count of ways reaches exactly one. Behind the board, how-many-ways-are-left is always ticking.

In the app, one new tip arrives for each day you play.

▶ Try 50 rounds in your browser A free demo, no install. All 2,000 rounds are in the app.