Girandola Sudoku – Medium

Girandola Sudoku

Girandola Sudoku is a 9x9 Sudoku variant with an additional marked group. The marked cells form a windmill-like pattern. The name Girandola means windmill or vortex roughly.

The normal Sudoku rules apply unchanged. Additionally, the nine Girandola cells must contain the numbers 1 to 9 exactly once. These cells are dispersed in the grid, connecting distant areas.

Basic Rules

• Each row contains the numbers 1 to 9 exactly once.
• Each column contains the numbers 1 to 9 exactly once.
• Each 3x3 block contains the numbers 1 to 9 exactly once.
• The nine marked Girandola cells form an additional region.
• This Girandola region also contains the numbers 1 to 9 exactly once.
• The given numbers must not be changed.

Strategies for Solving

1. Treat the Windmill as a separate region

The Girandola cells are treated as an additional Sudoku region. In this complete example grid, the Girandola region is almost fully filled.

Already, the marked Girandola cells contain 2, 3, 4, 5, 6, 7, 8, and 9. The only missing number is 1. Therefore, the middle Girandola cell in row 5, column 5 must be a 1.

2. Do not consider Girandola cells in isolation

A Girandola cell is always part of a row, column, block, and Girandola region. This creates useful combinations. If a candidate seems possible in normal Sudoku logic, it can still be excluded by the Girandola region.

3. Note missing numbers of the Girandola region

Since the marked cells are not directly adjacent, keep an eye on the missing Girandola numbers separately. After each entry in a marked cell, this list changes.

Typical Solving Process

1. First, solve obvious normal Sudoku steps.
2. Then check all marked Girandola cells as a connected region.
3. Note the missing numbers of the Girandola region.
4. Consistently eliminate these numbers from other Girandola cells if they are impossible there due to row, column, or block.
5. Use each Girandola entry again for the normal Sudoku areas.

Common Mistakes

• Relying on guessing too early instead of using the additional rule as a safe exclusion.
• Only checking rows and columns and overlooking the special marking of the puzzle.
• Entering a number that fits locally but violates the special rule.
• Not updating candidates after each new entry.
• Misreading a mark or applying it to the wrong cells.

Tips for Beginners

• Start like a normal Sudoku with well-filled rows, columns, and regions.
• Then check the special rule specifically. Often, early safe exclusions arise here.
• Always ask: which numbers are truly allowed and which are excluded by a rule?
• Enter a number only when it is unambiguously derivable.
• If stuck, change your perspective: from rows to columns, from regions to the special rule, or from individual cells to candidates.

Girandola Sudoku depends on connecting distant cells. Those who consistently keep track of the windmill region often find safe entries that are not visible in a normal Sudoku grid yet.