Sudoku is a logic puzzle where you fill a 9x9 grid with numbers. No math required, just reasoning. This guide walks you through our game interface and gives you strategies to tackle even the hard puzzles.
The basic rules
The goal is simple: fill every empty cell with a number from 1 to 9. But there are constraints.
- Each row must contain the numbers 1 through 9, with no repeats.
- Each column must contain the numbers 1 through 9, with no repeats.
- Each 3x3 box must contain the numbers 1 through 9, with no repeats.
Understanding the grid
The puzzle board shows a 9x9 grid divided into nine 3x3 boxes. Cells have different visual states to help you track your progress.
These are the starting numbers given by the puzzle. They appear in a darker color and cannot be changed. Use them as anchors for your solving.
Empty cells where you place your answers. Tap or click a cell to select it, then choose a number from the number pad.
When you select a cell, the game highlights its row, column, and 3x3 box. This helps you see which numbers are already taken in those areas.
If you place a number that violates the rules, the cell turns red. You lose a chance when this happens. Correct cells show in green.
Game controls
The sidebar shows your current game status. Keep an eye on these as you play.
Score
Your score increases with each correct placement. Harder difficulties give more points per cell. Try to finish with the highest score possible.
Timer
Tracks how long you have been working on the current puzzle. Challenge yourself to beat your previous times.
Chances (hearts)
The number of chances depends on difficulty: easy gives you 5 hearts, medium gives 3, and hard gives just 1. Each wrong answer costs one heart. Lose all hearts and the game ends. On easy and medium, you can use a second chance to continue.
The number pad
Below the game stats, you will find the controls for entering and managing numbers.
Select a cell on the grid first, then tap a number to place it. The number goes into the selected cell immediately.
Made a mistake? Hit undo to reverse your last action. You can undo multiple times to step back through your moves.
Changed your mind about that undo? Redo brings back the action you just reversed.
Removes the number from the selected cell. Useful when you want to clear an entry and try something else.
Difficulty levels
Choose your challenge at the top of the screen. Each level changes how many numbers the puzzle starts with.
- Easy: More starting numbers, good for learning the mechanics.
- Medium: Fewer clues, requires some logical deduction.
- Hard: Minimal starting numbers, demands careful analysis and pattern recognition.
Tips for hard difficulty
Hard puzzles will not give you obvious answers. You need to work for them. Here is what helps.
- Scan the entire grid before placing any number. Look for rows, columns, or boxes that are almost complete.
- Focus on one number at a time. Pick a number like 7 and find every cell where it could possibly go.
- When a cell could hold multiple numbers, move on. Come back after you have more information.
- Check the 3x3 boxes first. They often reveal answers faster than scanning long rows or columns.
- Take breaks if you feel stuck. A fresh look often reveals patterns you missed before.
Second chance
On easy and medium difficulty, if you lose all your hearts, you get one opportunity to continue playing. Hard mode does not offer this, so be extra careful with your guesses.