A calm place to learn Sudoku. Start with the given digits, scan each row, column and box, and fill a cell only when one number fits.
First-time players and anyone who wants a relaxed logic puzzle.
Look for a row, column or 3×3 box with many given digits. Eliminate the numbers already present and write the remaining candidates in empty cells. A cell with one candidate is a naked single.
On a keyboard, use the arrow keys to move between cells and N to toggle notes. Read the beginner guide or try a worked naked-single example.