How to play

• Every row, every column and every three-by-three box must contain the digits one to nine exactly once.
• The given digits are fixed; the ones you enter are shown in blue.
• Notes mode writes small candidates into a cell instead of an answer.
• Conflicting digits are highlighted in red as soon as they appear.
• A hint fills one correct cell and adds thirty seconds to your time.

Tips

• Start with rows, columns and boxes that already have the most digits.
• If a digit can go in only one cell of a box, it goes there — even when that cell has several candidates.
• Write pencil marks only where you already narrowed things down; a grid full of notes hides the answer.
• When you get stuck, scan one digit across the whole grid instead of staring at one cell.