All Sudoku Variants
9×9 · Constraint

Rossini Sudoku

An arrow outside a row or column shows whether its first three cells, counting inward, rise or fall in order.

3 7 9 8 2 9

An example Rossini puzzle: the arrow on column 2 says its first three cells strictly increase inward — 3, 7, 9.

Rossini Sudoku places an arrow outside some rows and columns. The arrow tells you whether the first three cells — counting inward from that edge — are strictly increasing or strictly decreasing, in the direction the arrow points. Rows and columns with no arrow carry no ordering clue at all.

The rule: the arrow orders the first three cells

An arrow pointing inward means read the three nearest cells in that direction and they must climb (or fall) step by step. Below, an "increasing" arrow sits beside a row whose first three cells rise: 2, 5, 8.

▸ 2 5 8

An increasing arrow: the first three cells rise — 2 < 5 < 8.

A worked example, step by step

Take a row with an increasing arrow and no givens yet.

▸

Step 0. An increasing arrow beside an empty row.

Step 1 — it's a rising chain of three. The first three cells must strictly increase, exactly like a three-cell thermometer. That means the first can be at most 7 (it needs two larger digits after it) and the third at least 3 (it needs two smaller before it).

▸1–72–83–9

Step 1. The rising chain gives each of the first three cells a window: 1–7, 2–8, 3–9.

Step 2 — tighten with the grid. Those windows already cut the candidates hard, and they interact with the rest of the row at once: if the row's 1 is known to lie elsewhere, the first cell climbs to 2–7, and so on. A single arrow, plus a few placed digits, often nails all three cells.

Solving strategy

  • Treat the arrow as a short thermometer. An increasing arrow is a rising three-chain; a decreasing one falls.
  • Push from both ends. The near cell takes the smallest window, the far cell the largest — meet in the middle.
  • Combine with the box. The three cells sit in the border box, so its other digits quickly finish the ordering.
  • Feed the grid. Each digit an arrow fixes behaves like a given for its row, column and box.

Common mistakes

  • Reading the direction wrong. The order follows the arrow; flip it and every deduction inverts.
  • Ordering more than three cells. A Rossini arrow only governs the nearest three cells.
  • Allowing equal steps. The three cells are strictly increasing or decreasing — never a plateau.
  • Forgetting ordinary Sudoku. The three cells still can't repeat a digit in their row, column or box.

Can I play it here?

Not yet — Rossini Sudoku isn't one of the puzzle types SudokuStreak generates for now. But you can learn its rules above, and there's plenty here to sink your teeth into meanwhile: