Hyper Sudoku
Hyper Sudoku adds four extra 3×3 windows to the classic 9×9 board, and each window must also contain every digit from 1 to 9 once. On this site the windows cover rows 2 to 4 and 6 to 8, in columns 2 to 4 and 6 to 8, so they overlap the ordinary boxes.
The board has four levels, Easy to Expert, with 150 stored puzzles at each, and no Evil level.
Where are the windows?
Number the rows and columns 1 to 9 from the top left. The four windows are the 3×3 blocks whose corners are at rows 2 and 4 or 6 and 8, and columns 2 and 4 or 6 and 8. The top-left window, for instance, runs from row 2 to row 4 and from column 2 to column 4. Each window straddles four of the ordinary boxes, so it is not aligned with the grid the way a box is. The table on the rules page labels all four, and the controls page covers input.
Together the windows cover 36 of the 81 cells. The cells in the middle row, the middle column and the outer ring are not in any window. The center cell is one of them.
How does this change what a cell can see?
A cell outside the windows still has twenty peers, as in classic Sudoku. A cell inside a window sees the cells of that window as well. The maximum is twenty-four peers, for cells such as row 4, column 4, which share their window with cells that are not already in the same row, column or box. Compared with the diagonal board, where the center cell sees thirty-two, the windows add less to any one cell, but they add to more cells.
What do the puzzles look like?
The site stores 150 puzzles at each of Easy, Medium, Hard and Expert. They have between 15 and 21 givens, averaging 18.0 to 18.4, which is about six fewer than the classic board’s average of roughly 24.5. Every puzzle is verified to have exactly one solution. No Evil puzzle was produced, because every generated hyper puzzle could be solved at Expert or below, and the site does not label a puzzle with a level it has not earned.
Which techniques does it favor?
The stored data for this board shows a distinctive profile. With 150 puzzles per level:
- Medium: naked pairs appear in 65% of puzzles, against 28% on the classic board, and hidden pairs in 37%, against 11%.
- Hard: naked triples are used in 85% of puzzles, against 58% on classic, and naked pairs in 75%. X-Wing appears in only 16%, compared with 46% on classic.
- Expert: simple coloring appears in 91% of puzzles and XY-Wing in 32%.
The pattern is that set-based techniques, naked pairs and naked triples, are needed more often here than on the classic board, while X-Wing is needed less. This page reports the pattern without explaining it. A reasonable guess is that the windows add more cells to each house’s interactions, so small sets form more easily, but the data does not show why.
A solving routine for hyper puzzles
- Mark the windows first. Before you begin, find the four windows on the grid, since forgetting one is the most common slip on this board.
- Add the windows to your scan. When you look for a hidden single, check the windows as well as the rows, columns and boxes. A digit that has only one cell left in a window goes there.
- Work the overlaps. A cell in a window and a box is constrained by both. If a digit is confined, within a window, to cells that share a row, it can be removed from the rest of that row.
- Expect pairs and triples. Write notes early, since the Medium and Hard levels lean on sets of cells with shared candidates.
- Save the center for last. It is outside the windows and only sees its row, column and box, so it is often resolved by the cells around it.
What should you learn first?
If you are aiming at Medium and Hard on this board, make sure the pair and triple lessons are solid. The pencil marks guide explains how to keep notes accurate, which matters when many cells carry two or three candidates. For Expert, learn simple coloring first, since 91% of Expert puzzles here use it. The strategy guide sets out what to learn level by level for the classic board, and the lessons carry over.
How is it different from the diagonal board?
Both add houses, but they add them in different places. The diagonal board adds two long lines that cross the whole grid. This board adds four compact blocks that sit inside the grid. The solving feel differs accordingly: diagonals are scanned like long rows, while windows are scanned like extra boxes. If you would like a rule that restricts cells in pairs and not in groups, try anti-knight, and for houses that change shape instead, irregular Sudoku.
The games hub lists every board, and the home page has the classic game if you would like to compare.