Neighbourhood Watch
(Published on 15. January 2026, 00:00 by SennyK)
Puzzle with modifier cells and region sum lines, estimated difficulty 2.5* :-)
I hope you will enjoy and I would be really grateful for all the comments and ratings.
Normal sudoku rules apply.
Modifiers: There is exactly one modifier cell in each row, column, and 3x3 box. Digits do not repeat in the modifier cells. Value of a modifier cell is the sum of the digits of its (up to 4) orthogonal neighbours, regardless of the digit in the modifier cell itself. Value of the remaining cells is equal to their digit.
Region sum line: Box borders divide a blue line into segments which have the same sum of values. Different lines may have different sums.
X: Values in cells joined by an X sum to 10. Not all Xs are necessarily given.
Kropki dots: Values in cells joined by a white dot are consecutive. Values in cells joined by a black dot are in a 1:2 ratio (i.e., one value will be double the other). Not all dots are necessarily given.
Recommended for you: Modified Flat Mates
If you liked this puzzle, I recommend trying out my other puzzles: The Erica Series:★☆☆☆☆: 1, 2, 4, 5, 6, 12, 15, 17, 23, 26, 27
★★☆☆☆: 3, 7, 8, 10, 11, 13, 14, 16, 18, 20, 24, 25, 29, 30
★★★☆☆: 9, 19, 21, 22, 28 Shading/Ying-Yang:
★★☆☆☆: Pretty Odd Shaded Area
★★★☆☆: (+5)-Yang, Negative 8 YY
★★★★☆: (Yin)German Pairrows
★★★★★: Why-Why? Fog of War:
★☆☆☆☆: Erica 12, Erica 17
★★☆☆☆: It's What You Do in the Dark That Puts You in the Light, Find It All, What the Fog?, Erica 20, Erica 29
★★★☆☆: Broken Flashlight in the Dark Pencil Puzzle/Sudoku Hybrid:
★★☆☆☆: Masyu (Short) Sudoku
★★★☆☆: Tetromino Sudoku
Various Puzzles:
★☆☆☆☆: Blown Fuses in Electrical Installation, Let Me Introduce Myself, French Wrench, GAS Regional Constraints
★★☆☆☆: Symmetrical Fan, Night Club, Important Hour on the Clock, What Was the Sum Again?, Disgroup Joints, 10-Arrows, Antiking Dutch Skyscrapers, (Not so) Little Killers, Indexing Sword
★★★☆☆: Cops & Robbers, Positive Symmetry, Doppelgänger Killer 1-25, Region Whisper Line, Christmas Chaos, Modified Flat Mates
★★★★☆: Liars. Liars Everywhere., Sandwiched XV Squishmates, Fireworks 2025, (Yin)German Pairrows
Solution code: Digits in modifier cells in normal reading order: left to right, top to bottom.
Comments
on 17. January 2026, 09:38 by VitP
goldilocks puzzle
on 16. January 2026, 04:55 by chinesemaster
Very smooth!
on 15. January 2026, 19:26 by dzamie
Had some really interesting logic to it! I like how basically all of the rules wind up being used consistently throughout the puzzle.
Definitely at least a 3* difficulty imo
on 15. January 2026, 15:52 by ThePedallingPianist
Really smooth puzzle, filled to the brim with interesting logical deductions!
on 15. January 2026, 10:50 by Snookerfan
Great puzzle with a complex modifier that gives quite hard and mathy logic! I could imagine a absolutely horrificly difficult puzzle with this modifier, so keeping it doable is a setters achievement. Very enjoyable, thanks.
on 15. January 2026, 08:48 by Elliott810
Absolutely brilliant puzzle! Take a bow and thank you:)
on 15. January 2026, 02:42 by Exigus
I liked it. Not easy but not as hard as it may seem from the ruleset. Thanks!
