Kakuro

Kakuro looks like a crossword, but the "words" are runs of white cells and the clues are sums. Each black clue cell has a number for the run to its right (top-right number) and/or the run below it (bottom-left number). Fill every white cell with a digit from 1 to 9 so that each run adds up to its clue, with no digit repeated inside a run.

Each grid is generated and checked by a solver; when needed, the generator adjusts the digits until the puzzle has exactly one solution. Very occasionally a cell starts filled in.

1. Select a white cell and type a digit (or use the pad).
2. The digits in each run must add up to its clue.
3. Digits may not repeat within a run.
4. Use Hint to reveal a cell and Undo to step back.

• Memorise the unique sums: 3 in two = 1+2, 4 in two = 1+3, 16 in two = 7+9, 17 in two = 8+9, 6 in three = 1+2+3, 24 in three = 7+8+9.
• Cross the runs. A cell belongs to an across and a down run; it must suit both.
• Use the largest and smallest digits. A long run with a small total can't contain a 9.