Little Killer Sudoku (PuzzleMadness)

About Little Killer Sudoku (PuzzleMadness)

The standard rules apply: 1 to 9 once in every row, column and 3x3 box. Outside the grid sit clues made of a number and a small diagonal arrow. Follow the arrow into the grid and on to the far edge: the digits in every cell along that diagonal add up to the clue. In the site's example, a 19 on the left edge with an arrow pointing down and to the right sums the cells on that diagonal. Unlike the cages of a killer sudoku, digits may repeat along a diagonal, as long as the normal rules are kept.

Short diagonals near the corners are the quickest clues, since a diagonal of two or three cells with a small or large total has very few fillings. Longer diagonals cut across several boxes, so they combine well with what you already know from the rows and columns.

The grid works like every sudoku on PuzzleMadness: number buttons above and below it, an eraser, and a pencil mode for candidate digits. On a keyboard, the number keys enter digits, the arrow keys move between cells, Ctrl, Shift or Alt with a number adds a pencil mark, and Delete or Backspace clears a cell.

PuzzleMadness is a free puzzle website run by Dewi, a software developer who started out making games for the PlayStation 2, Nintendo Wii and DS and now builds the site as a hobby. It carries dozens of puzzle types, from classic sudoku to newer logic grids, and each one gets its own dated puzzle every day at each difficulty. Little Killer Sudoku comes in Easy, Medium, Hard and Tough versions plus a Mixed page, and the same day's Little Killer Sudoku puzzle is shared by everyone who opens it.

The site checks your grid as you go and tells you when it is finished; it does not publish solutions. Each completed puzzle earns a score, and scores feed a monthly and an all-time Little Killer Sudoku leaderboard, where only your best attempt at a puzzle counts. Older days stay in the archive, so a missed puzzle can still be played later and still counts toward the current month. Playing needs no account; a free registration gives you a username on the leaderboards and a cloud save. The pages carry adverts.

How to play Little Killer Sudoku (PuzzleMadness)

1. Open today's Little Killer Sudoku page on PuzzleMadness and choose a difficulty from the menu above the grid.
2. Click a cell and enter a digit with the number buttons above and below the grid or with the keyboard; the eraser button clears a cell.
3. Fill every row, column and 3x3 box with the digits 1 to 9, each once.
4. For each clue outside the grid, follow its arrow along the diagonal and make the digits on it add up to the number.
5. Turn on pencil mode (the pencil button, or Ctrl, Shift or Alt with a number key) to jot candidate digits in a cell.
6. The site tells you when the grid is complete and adds your score; registered players appear on the leaderboards.

Tips

• Start with the short diagonals near the corners; a two-cell diagonal summing to 3 can only be 1 and 2.
• Digits can repeat on a diagonal, so do not rule out a pair just because the two numbers are equal.
• Long diagonals pass through three boxes; split their totals using digits you already know.
• Missed a day? Earlier puzzles are in the archive, and finishing one still counts toward this month's leaderboard.

Questions