Kropki Sudoku (PuzzleMadness)

Kropki Sudoku keeps the usual sudoku rules: each row, column and 3x3 box holds the digits 1 to 9 once. On top of that, dots sit on some of the borders between neighbouring cells. A white dot means the two digits differ by one, such as 4 and 5. A black dot means one digit is twice the other, such as 3 and 6. The pair 1 and 2 could take either colour. The missing dots matter as much as the printed ones: two neighbours with no dot between them are neither consecutive nor in a 1:2 ratio.

Because of the dots, the grids start with fewer given digits than a classic sudoku of the same difficulty. The Medium grid for 28 October 2026, for example, starts with 25 given digits and dots spread across every box.

PuzzleMadness is a free puzzle website run by Dewi, a software developer who started out making games for the PlayStation 2, Nintendo Wii and DS and now builds the site as a hobby. It carries dozens of puzzle types, from classic sudoku to newer logic grids, and each one gets its own dated puzzle every day at each difficulty. Kropki Sudoku comes in Easy, Medium, Hard and Tough versions. The Mixed page holds a fifth grid of its own, and its level changes from day to day. On 28 October 2026 it was a Medium grid with a different start from the Medium page's. Every grid is shared by everyone who opens it that day.

The site checks your grid as you go and tells you when it is finished; it does not publish solutions. Each completed puzzle earns a score, and scores feed a monthly and an all-time Kropki Sudoku leaderboard, where only your best attempt at a puzzle counts. Older days stay in the archive, so a missed puzzle can still be played later and still counts toward the current month. Playing needs no account; a free registration gives you a username on the leaderboards and a cloud save. The pages carry adverts.