Between Line Sudoku (PuzzleMadness)

About Between Line Sudoku (PuzzleMadness)

The normal rules of sudoku apply, with 1 to 9 once in every row, column and 3x3 box. Each Between line has a circle at both ends. The digits in the cells along the middle of the line must all lie strictly between the two circled digits, so a line from a 2 to a 7 can only hold 3, 4, 5 and 6 in its middle, and never 2 or 7 themselves. Either end can be the larger one.

The ends of a line are usually far apart in value, since a long line needs room for its middle digits: a line with three middle cells needs ends at least four apart. Circles cannot hold a digit equal to any middle cell, which also rules out 1 and 9 in the middle of any line. Today's Medium grid, for example, has more than a dozen lines, some short and one running diagonally across most of the grid.

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

1. Open today's Between 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. On each Between line, make every digit in the middle of the line strictly larger than one circled end and strictly smaller than the other.
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.

Screenshots

Tips

• 1 and 9 can never sit in the middle of a line; they often belong in the circles.
• Count the middle cells: with n different digits needed in the middle, the circled ends must be at least n + 1 apart.
• A given digit in the middle of a line tells you one circle is above it and the other below.
• Missed a day? Earlier puzzles are in the archive, and finishing one still counts toward this month's leaderboard.

Questions