Cracked Sudoku

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Sudoku without a grid: 81 cracked cells, groups and coloured runs.

on danielchasehooper.com

Today's Cracked Sudoku board on 19 October 2026: irregular polygon cells with givens, thick group outlines, coloured run lines and the number pad

Cracked Sudoku keeps the rules of sudoku but throws out the grid. The 81 cells are irregular polygons, as if the board had cracked, split into nine outlined groups, and instead of rows and columns there are coloured run lines along which no number may repeat. A new layout comes out every day.

About Cracked Sudoku

Cracked Sudoku is a sudoku variant by Daniel Hooper, who wrote about how he built it in March 2025. The board is generated from a Voronoi diagram, so every puzzle has a different shape: 81 cells of many sizes and numbers of sides, grouped into nine dark-outlined regions of nine cells.

Rows and columns are replaced by runs, strips of two to nine cells shown as coloured lines. A run goes through neighbouring cells and carries on through the opposite side of each cell, ending at cells with an odd number of sides. The rule is the same as classic sudoku: fill every cell with 1 to 9 without repeating a number in a group or along a run. The line colours only help tell runs apart.

The page loads one puzzle per day from a pregenerated list of more than 1,300 layouts, counted from 4 March 2025 by the date in Pacific Time, so everyone solves the same layout, and it tells you to come back in 24 hours. Your progress is kept in the browser, so you can leave and finish later the same day. There are tools for pencil marks, undo, checking and restarting. It suits sudoku players who know the classic grid well and want the same logic in an unfamiliar shape.

How to play Cracked Sudoku

Open the page to load today's cracked board.
Select a cell and enter a number from 1 to 9, or use Pencil for candidates.
Make sure no number repeats inside a dark-outlined group of nine cells.
Make sure no number repeats along any coloured run line.
Use Check to test your progress and Undo or Restart if you go wrong.

Screenshots

A Cracked Sudoku board: irregular polygon cells with givens, thick group outlines and coloured run lines

Tips

Follow one run at a time: short runs of two or three cells are often the quickest to resolve.
Cells where many runs cross are heavily constrained, so start there.
Pencil in candidates early; the irregular layout makes it hard to keep them in your head.
Runs end at odd-sided cells, so check where each line stops before assuming two cells share a run.