How to Play Sudoku

🎯 1. Fundamental Rules of Sudoku

Sudoku is played on a 9x9 grid divided into nine 3x3 sub-grids (or "boxes"). Some cells start pre-filled with clue numbers. Your objective is to fill the remaining empty squares so that:

• Each row contains the numbers 1 through 9 with no repeats.
• Each column contains the numbers 1 through 9 with no repeats.
• Each 3x3 block contains the numbers 1 through 9 with no repeats.

No mathematical arithmetic is required: every solution is determined purely through deduction and logical elimination.

🕹️ 2. Clean, Readable Board Controls

Our board is purposefully engineered to eliminate skewed perspective, blurry angles, and eye strain:

• Selecting a Cell: Tap or click any cell. The active cell highlights with a glowing cerulean border.
• Visual Scanning: Whenever a cell is selected, all cells in the same row, column, and 3x3 block receive a gentle background tint. In addition, all other instances of that same number highlight in warm neon rose so you can scan the board in milliseconds.
• Placing Digits: Click any number (1–9) on the keypad or type on your keyboard.

✏️ 3. Using Pencil Notes & Rewarded Hints

• Pencil Notes: Toggle "Notes" mode (N key or UI button) to jot down small candidate numbers in tricky cells. When you confirm a final digit in any cell, candidate notes in the matching row, column, and 3x3 box are pruned automatically!
• 24-Hour Free Hint Economy: Every player receives 2 free hints every 24 hours (tracked via cookies & browser storage across all your games). After using your 2 daily free hints, every hint strictly requires watching a brief sponsor ad. If no ad is completed or available, no hint is given.

🧠 4. Winning Logic Strategies

1. Naked Single: If a cell has 8 of the 9 digits present in its intersecting row, column, and 3x3 block, there is only one possible digit remaining.
2. Hidden Single: If a number can only legally be placed in one specific cell within a 3x3 block (even if that cell has other candidate notes), that number belongs there.
3. Cross-Hatching: Scan parallel rows or columns containing the same digit to quickly rule out columns or rows in neighboring blocks.

⌨️ 5. Keyboard Shortcuts