Controls

You solve Sudoku by placing digits into empty cells. On a phone, tap an empty cell, then tap a number on the pad below the grid. On a laptop, click a cell and type the digit on your keyboard, or move between cells with the arrow keys instead of the mouse.

A couple of details are easy to miss the first time:

• Erasing a digit has no dedicated button. Tap or click the same number again to clear it, or press Backspace, Delete, or 0 on a keyboard.
• Pencil marks let you note the possible numbers for a cell when you are not sure yet. Tap Notes to switch into marking mode, tap in the candidates, then tap Notes again to go back to placing real answers.
• The three rules are all you need: each digit 1 to 9 appears once per row, once per column, and once per 3x3 box. Every answer follows from those.

You finish a puzzle when every cell is filled and no digit repeats in any row, column, or box.

The puzzles come in rising difficulty across eight levels, from open grids with many clues to sparse ones that need careful deduction. A Help button explains the rules, and Hint fills in the next cell plain logic can solve and tells you why.

Tips

• Start with the most crowded rows, columns, and boxes. The more numbers already placed nearby, the fewer options a cell has, so those are the easiest cells to solve first.
• Hunt for cells with only one possible number. If a spot can only be a 4 because every other digit already appears in its row, column, or box, that 4 is certain, no guessing needed.
• Use pencil marks on the tough grids. Writing down the candidates for a cell turns a fuzzy problem into a visible one, and patterns you would otherwise miss start to stand out.
• Look for a number that fits only one spot in a box. Sometimes a box has just one place a 7 can legally go, even if that cell had other candidates. Scanning by number catches these.
• Never guess. Every puzzle here has a single solution reachable by logic, so if you are guessing, there is a deduction you have not spotted yet. Backing into an answer usually leads to a dead end.
• Take a break when you are stuck. Fresh eyes catch the cell you stared past. Coming back a minute later often solves what felt impossible.

Frequently asked questions