Yamanote (Loop Japanese Sums Sudoku)
(Published on 10. February 2026, 09:00 by Agent)
This is the puzzle I set for proxz14 as part of the Secret Santa gift exchange. I hope you enjoy!
Rules
- Place the digits 1-9 once each in every row, column, and 3x3 box.
- Shade some cells so that clues outside the grid give the sum of digits in each contiguous sequence of unshaded cells in the respective row or column. For a given row or column, either all clues or no clues are given.
- Each letter represents a different digit from 0 to 9. A question mark may represent any digit from 0 to 9, but for double digit numbers, the first digit may not be 0.
- Draw a one-cell-wide loop of orthogonally connected cells. The loop may not touch itself orthogonally, but may touch diagonally.
- Each set of three adjacent digits along the loop must include an unshaded odd digit, an unshaded even digit, and a shaded digit.
- Cells separated by a white dot must contain consecutive digits, and they must both be on the loop.
Solution code: Digits in shaded cells in row 1 (from left to right) then in row 3 (from left to right)
Comments
on 11. February 2026, 11:05 by Snookerfan
Fantastic puzzle! I wish I read the rule about the loop can not touch itself orthogonally sooner, that would have saved a lot of time. Thanks
on 11. February 2026, 08:35 by Piatato
Great fun! Delightful ruleset and a smooth and rewarding solve!
on 10. February 2026, 14:09 by Christounet
Great fun! The opening setup is awesome. Thanks :)
on 10. February 2026, 12:01 by .proxz14
What an incredible gift to receive! The very moment I saw the grid and recognised it as a JSum puzzle I already knew this was going to be a good time, but it got even better as the solve went on. It's a rare example of a Japanese Sums puzzle that can keep a constant level of difficulty from its first deduction to the final one. Thanks Santa :)
