GridWits

Surface Sum

Expert Used by Smart Hint

Two overlapping groups of runs differ by exactly one cell — subtracting their clue totals determines that cell's digit outright.

16 11 13 20

How it works

  1. Add the two down clues: 16 + 11 = 27. That's the exact total of the four tinted cells.
  2. Now add the two across clues: 13 + 20 = 33. Those two runs cover the same four cells — and one cell more, the one hanging off the end of the lower row.
  3. Everything in the tinted block cancels between the two sums, so the leftover cell is 33 − 27 = 6.
  4. No candidate lists needed, no combination table — just clue arithmetic over a region whose two directions don't quite line up. Hunt for these wherever a row runs one cell past the columns beside it.