Evil Sudoku - The Ultimate Challenge
Evil level sudoku is the pinnacle of sudoku puzzles. With only 17-20 starting clues, you need all advanced techniques to tackle this challenge.
What Makes Evil Sudoku So Difficult?
The evil level is distinguished by its minimal number of starting clues and the complex patterns needed to solve the puzzle. Where an average puzzle has 32-35 clues, here you get only 17-20 numbers to start with.
17 clues is the mathematically proven minimum for a sudoku with one unique solution.
What Techniques Do You Need?
X-Wing
A pattern where a candidate appears in exactly two cells in two rows, in the same columns.
Swordfish
An extension of X-Wing with three rows and three columns for more complex eliminations.
XY-Wing
A pattern with three cells that each share two candidates in a specific configuration.
Forcing Chains
Advanced logical chains that eliminate possibilities by following hypothetical scenarios.
Why Is 17 the Minimum Number of Clues?
In 2012, mathematicians proved that every valid sudoku with a unique solution must have at least 17 starting clues. Puzzles with fewer clues always have multiple possible solutions, making them unsuitable as true sudoku.
Tips for Evil Puzzles
- Take your time - rushing leads to mistakes that are difficult to recover from.
- Always use pencil marks and update them systematically.
- First master the advanced techniques on expert level puzzles.
- Take regular breaks to return with fresh eyes.
Average Solving Time
90+ min
Even experienced players often need more than an hour and a half