Killer Sudoku is a challenging variant of classic Sudoku that combines traditional rules with arithmetic constraints. Here's how to play:

Basic Rules:

• Classic Sudoku Rules: Each row, column, and 3×3 region must contain the digits 1 through 9 exactly once.
• Cages: The grid is divided into "cages" outlined by dashed lines.
• Cage Sums: The small number in the corner of each cage indicates the sum that all digits in that cage must add up to.
• No Repeats in Cages: Digits cannot repeat within the same cage.
• Empty Grid: Unlike classic Sudoku, the grid starts completely empty.

Solving Tips:

• Use the "Rule of 45": each row, column, and 3×3 region totals 45 (1+2+3+4+5+6+7+8+9).
• Start with small cages with limited sums (e.g., a 2-cell cage with sum 3 can only contain 1 and 2).
• Look for cages with unique combinations.
• Use cross-constraints between cages and Sudoku rules.

Classic Sudoku

The original Sudoku game with partially filled grids. Perfect for beginners and experts with 5 difficulty levels. To access it, click here.

Skyscraper game

The skyscraper game is a puzzle derived from Sudoku. Each grid is composed of NxN cells and on the side of this grid are clues. The goal is to place a skyscraper in each cell. Each skyscraper has a height between 1 and N and tall skyscrapers hide smaller ones placed behind them. To access it, click here.

SudokuX

A variant of Sudoku, SudokuX introduces additional difficulty by requiring that each main diagonal also contains each digit only once. To access it, click here.