Place a digit 1-9 into each empty cell. The number in a grey cell indicates the sum of the digits placed in cells the adjoining arrow passes through. The digits within an arrow must be placed in ascending order (the highest digit is at the sharp end of the arrow). No digits may repeat within a row/column.
(Rules and example from WPC 2015 IB)
History of the puzzle
Origin unknown. First appearance known so far is from Minako Sakai's (Japan) puzzle in WPC 2015/Round 3. Most likely first appeared as a submission to Puzzler magazine from her.
Has similar elements to Sudokuro and Thermo Sudoku.
Appearances in the past WPCs
- WPC 2015/Round 3 by Minako Sakai