About this game
Sudoku is a number puzzle that rewards patience and careful logic rather than arithmetic. The board is a nine by nine grid split into nine three by three boxes, and a few cells are already filled in. Your job is to complete the rest so that every row, every column and every box contains the digits 1 to 9 exactly once. This version lets you choose Easy or Hard. Easy grids start with around 30 given numbers, so you can make steady progress by looking for cells that have only one possible answer. Hard grids give you only 24, which means you have to reason further ahead. A timer starts when you begin and stops when the last cell is correct, so speed and accuracy both matter. A number that does not match the solution turns red straight away, which helps you catch a slip before it spreads. Your best time for each difficulty is saved on your device, and the fastest solves can earn a place on the global leaderboard.
Controls
- Keyboard: click a cell, then press 1 to 9 to fill it. Use the arrow keys to move between cells, and Backspace, Delete or 0 to erase.
- Phone or tablet: tap a cell, then tap a number on the pad below the grid. The erase key clears the cell.
- Selecting a cell shades its row, column and box so you can see which numbers are already used.
- Choose EASY or HARD to start, or use the New Easy and New Hard buttons at any time for a fresh puzzle.
Tips and strategy
- Start with the digit that already appears most often. Scan each box and ask where that digit is still allowed; often only one cell is left.
- Look at nearly full rows, columns and boxes first. A line with eight numbers has exactly one answer left.
- Use the highlighting. Selecting a cell shades its row, column and box, so you can see at a glance which numbers are already taken.
- When a cell has only one number that is not blocked by its row, column or box, write it in. Each new number makes the next one easier to find.
- Trust the red warning. A red cell means the number does not match the solution, so fix it straight away instead of building on it.
- On Hard, do not guess to save time. Step back and study a different part of the grid, because a fresh area often unlocks the one you were stuck on.