Classic Sudoku Crazy

Crazy Classic Sudoku is our hardest setting: the sparsest boards we generate, built so the solve path runs through layered eliminations and long chains. Come warmed up. Every cell takes one of nine symbols: 123456789.

How to play Classic Sudoku

The board is a 9×9 grid divided into nine 3×3 boxes. Fill every empty cell so that each digit appears exactly once per row, column and box. Every puzzle we serve has a single valid solution.

• Each row contains the digits 1–9 exactly once.
• Each column contains the digits 1–9 exactly once.
• Each 3×3 box contains the digits 1–9 exactly once.
• Prefilled cells are fixed clues — everything else you deduce.

Crazy Sudoku tips

Crazy boards are solved by structure, not by luck:

• Chain candidates. Link strong relationships — units where a symbol fits only two cells — and follow where a contradiction propagates. Chains are the bread and butter of crazy boards.
• Solve regions, not cells. Target a whole box or line: enumerate its missing symbols and prove where each one must live before you touch the rest of the grid.
• Respect the mistake counter. Crazy punishes rushing. Verify each placement against row, column and box before committing, and when you do slip, reread the chain that produced the error.

About Classic Sudoku

Classic Sudoku is the puzzle as it has been played for decades: a 9×9 grid, the digits 1–9, and one rule repeated three ways. It is still the most-played logic game in the world, and the level most solvers use to measure their speed.

More Classic Sudoku levels

Classic Sudoku Easy · Classic Sudoku Medium · Classic Sudoku Hard · Classic Sudoku Expert

About Sudoku

Sudoku is a logic-based, combinatorial number-placement puzzle. In classic Sudoku, the goal is to fill a 9 x 9 grid with digits so that each column, each row, and each of the nine 3 x 3 subgrids that compose the grid contains all of the digits from 1 to 9. The puzzle setter provides a partially completed grid, which for a well-posed puzzle has a single solution.

About Sudokuing

Sudokuing(Sudoku'ing) is an online Sudoku gaming website that focuses on providing a user-friendly, variety of themed Sudoku puzzles for everyone to enjoy.