Kakuro is a crossword built from sums. Fill the white squares with 1–9 so that each horizontal run adds up to the number to its left, and each vertical run adds up to the number above it.

• No digit repeats inside a single run — that rule does the real work.
• A two-square run summing to 3 can only be 1+2; a two-square 17 can only be 8+9.
• Grey digits are given. Tap a square and type, or use the keypad.
• Notes lets you pencil in candidates; Check marks anything wrong.

Runs with extreme sums are the way in: solve those first, then use the crossings.