RegionSum Line Sudoku (PuzzleMadness)

About RegionSum Line Sudoku (PuzzleMadness)

The standard sudoku rules hold: every row, column and 3x3 box contains 1 to 9 once. Each grey line passes through two or more boxes. Split the line wherever it crosses a box border, and the digits in each piece must have the same sum: in the site's example one line splits into 2 + 5 + 8, 8 + 2 + 5, 4 + 2 + 9 and 2 + 4 + 9, all making 15. If a line leaves a box and later comes back into it, the two visits count as separate segments with their own sums.

The interesting cases are segments of different lengths. A single cell in one box must equal the total of two or three cells in the next, which caps those cells low and pushes the single cell high. Today's Medium grid, for example, has several long lines weaving through most of the boxes.

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

1. Open today's RegionSum 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. Split each grey line where it crosses box borders, and make the digits in every segment of that line add up to the same total.
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

• Compare segment lengths: a one-cell segment must equal the sum of a longer segment, so it is at least 3 when the other has two cells.
• A known segment total spreads along the whole line, so fill one segment completely and the rest become sum puzzles.
• Remember that a line re-entering a box makes a new segment, not part of the earlier one.
• Missed a day? Earlier puzzles are in the archive, and finishing one still counts toward this month's leaderboard.

Questions