Lockout Line Sudoku (PuzzleMadness)

About Lockout Line Sudoku (PuzzleMadness)

The ordinary sudoku rules hold, with 1 to 9 once in every row, column and 3x3 box. Each Lockout line has a diamond at both ends. The digits in the two diamonds must differ by 4 or more, and the digits on the cells in between are locked out of that range: they may not equal either end, nor fall between them. In the site's example, a line with 2 and 6 in its diamonds has 7 and 8 in the middle, both above the range 2 to 6.

It is the opposite of a Between line, which keeps its middle digits inside the range of its ends. Because the ends are at least 4 apart, a lockout range always swallows at least five digits, leaving only the low or high extremes for the middle cells; a diamond holding 5 forces the other diamond down to 1 or up to 9.

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. Lockout Line Sudoku comes in Easy, Medium, Hard and Tough versions plus a Mixed page, and the same day's Lockout Line 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 Lockout Line 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 Lockout Line Sudoku (PuzzleMadness)

1. Open today's Lockout Line 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. Make the two diamond digits at the ends of each line differ by at least 4.
5. Keep every digit in the middle of a line outside the range of its two diamonds, never equal to either end.
6. Turn on pencil mode (the pencil button, or Ctrl, Shift or Alt with a number key) to jot candidate digits in a cell.
7. The site tells you when the grid is complete and adds your score; registered players appear on the leaderboards.

Tips

• A diamond with 5 must pair with a 1 or a 9.
• With ends like 2 and 6, the middle can only use 1, 7, 8 or 9; work out the locked-out range before anything else.
• Long lines need many free digits outside the range, so their ends are usually close to one side, such as 1 and 5 or 5 and 9.
• Missed a day? Earlier puzzles are in the archive, and finishing one still counts toward this month's leaderboard.

Questions