Sudoku

🎯 Objective

Fill all 81 squares so the digits 1 to 9 appear exactly once in every row, every column and every 3x3 box. There is only ever one solution, and it can always be reasoned out.

📊 How you score

Your score is points, and higher is better. Every day has its own points ceiling that rises with the difficulty, so a Sunday grid is worth four times a Monday one and a fast Monday can never top the all-time board. Solve inside the day's grace period and you keep the whole ceiling; take longer and it decays gently from there. Boo can point out the next forced move up to 3 times a grid, and each hint costs a slice of that day's ceiling, so it is a real trade rather than a free answer. Slips cost a little too, capped so a wobbly patch never sinks a run. If a grid gets away from you entirely, Reset clears the board back to its clues and puts 2 minutes on your clock: your slips and hints stay on the record, and it is still your one attempt for the day. Solving on consecutive days builds your solve streak.

💡 Tips

• Scan for the digit that is already placed most often. The more copies on the board, the fewer squares are left for the next one.
• Work a box, a row and a column that all cross the same empty square. A digit ruled out by any one of them is ruled out for good.
• From Thursday on, pencil marks stop being optional. A square with only two candidates is the thread to pull.
• Two squares in a unit holding the same two candidates lock those digits away from every other square in that unit.
• Stuck? Tap Hint below the board. Three hints per grid, and each one names the rule that proves the move, then shows you the square and its digit, so you learn the pattern rather than just the answer.