🎯 Goal

The board is a 9×9 grid split into nine 3×3 boxes. Some cells start filled in (the “givens”). Your job is to fill in every empty cell so that each row, each column and each 3×3 box contains the digits 1 to 9 exactly once. Every puzzle has one — and only one — correct solution.

🕹️ Controls

• Tap a cell to select it, then tap a number on the pad to place it.
• Desktop: click a cell and press 1–9; use arrow keys to move, 0 / Backspace to clear, N to toggle notes.
• Given clues are locked and can't be changed.

🔦 Highlighting & helpers

• Selecting a cell highlights its whole row, column and 3×3 box so you can scan for what's missing.
• Every cell holding the same number as your selection is highlighted too — handy for spotting where a digit can still go.
• Any number that breaks a rule (a duplicate in a row, column or box) is flagged in red.
• The number pad shows how many of each digit are left, and greys out a digit once all nine are placed.

✏️ Notes, hints & mistakes

• Notes mode lets you pencil in small candidate numbers in a cell while you work out the possibilities.
• Hint fills the selected cell with the correct answer if you're stuck.
• Placing a wrong number counts as a mistake. Five mistakes ends the game — so double-check before you commit.

🔥 Difficulty & timing

• Easy, Medium and Hard change how many clues you start with — fewer givens means a tougher solve.
• A fresh, uniquely-solvable puzzle is generated every single game.
• The clock tracks your solve time, and your best time is saved per difficulty on your device.

💡 Tips

• Start by finding cells where only one number can possibly fit.
• Use the same-number highlight to sweep a digit across the board and see where it's forced.
• When a box, row or column has just one gap, fill it first — it often unlocks others.