Girandola Sudoku – Easy

Solve Girandola Sudoku: Rules and Strategies

Girandola Sudoku is a Sudoku variant. Nine marked cells form a windmill-like pattern across the entire Sudoku.

These nine cells are an additional area and contain the numbers 1 to 9 exactly once.

The goal is a fully filled, conflict-free puzzle. Each move must follow the visible clues and already confirmed entries.

Rules

• Each active cell contains exactly one number from 1 to 9.
• Each row contains the numbers 1 to 9 without repetition.
• Each column contains the numbers 1 to 9 without repetition.
• Each normal 3×3 block contains the numbers 1 to 9 exactly once.
• These nine cells are an additional area and contain the numbers 1 to 9 exactly once.
• Pre-given numbers are not changed.
• Each final entry must meet all rules simultaneously.

Orientation in the Grid

Rows are counted from top to bottom, columns from left to right. In a number pair, the first number indicates the row and the second the column; for example, (4,7) refers to the cell in row 4, column 7.

The examples show a specific intermediate state each. Blue markings indicate the assumptions used, red markings an exclusion, and green markings a confirmed result.

Basic Idea for Solving

Start with normal Sudoku units, but always check the marked additional areas as well. A candidate remains allowed only if it fits in all related units.

After each confirmed entry, it’s worthwhile to briefly review all affected units and clues. This creates a chain of small, understandable steps.

1. Complete an Almost Full Row

In the row unit 1, everything except cell (1,4) is filled. Visible are 1, 2, 3, 4, 5, 6, 7, 9; only 8 is missing from the allowed numbers.

Therefore, 8 goes in (1,4). The move requires no guess: the remaining values of the considered unit are fully visible in the image.

2. Complete an Almost Full Column

In the column unit 1, everything except cell (5,1) is filled. Visible are 1, 2, 3, 4, 5, 6, 7, 8; only 9 is missing from the allowed numbers.

Therefore, 9 goes in (5,1). The move requires no guess: the remaining values of the considered unit are fully visible in the image.

3. Fully Read the Relevant Area

In the 3×3 block 1, everything except cell (2,2) is filled. Visible are 1, 2, 3, 4, 5, 6, 7, 9; only 8 is missing from the allowed numbers.

Therefore, 8 goes in (2,2). The move requires no guess: the remaining values of the considered unit are fully visible in the image.

4. Use the Extra Area as a Complete Unit

In the Girandola area unit, everything except cell (5,5) is filled. Visible are 2, 3, 4, 5, 6, 7, 8, 9; only 1 is missing from the allowed numbers.

Therefore, 1 goes in (5,5). The move requires no guess: the remaining values of the considered unit are fully visible in the image.

5. Exclude a Repetition in the Extra Area

The number 5 already appears at (1,1) in the extra Girandola area. Therefore, the same value cannot occur again in the marked cell (5,5).

5 is struck through at (5,5). The diagram intentionally shows only this exclusion; the final value of the cell is additionally determined by its normal Sudoku units.

6. Locate a Number in the Extra Area

Several cells are open in the extra Girandola area unit. For the number 1, the other open positions are eliminated by their respective rows, columns or 3×3 blocks; only position (5,5) remains.

Therefore, 1 is entered at (5,5). This is a hidden single candidate: the cell itself may initially have multiple possibilities, but in the extra area, the number has only one place.

7. Combine Multiple Units in One Cell

At (1,4), several units are still incomplete. After the joint exclusion by all related rows, columns, and areas, only 8 remains.

The candidate set for (1,4) is thus {8}. Such single possibilities often arise only after all types of units are checked simultaneously.

Typical Solving Sequence

1. Fill in immediately complete rows, columns, and relevant areas.
2. Note only candidates that are allowed by all normal units for open cells.
3. Apply the additional rule of the puzzle type to these candidates.
4. Enter only conclusively justified values.
5. After each entry, revisit all affected units and clues.
6. Repeat the review until the grid is complete.

Common Mistakes

• Overlooking the marked extra area: A traditionally allowed candidate may already be present there.
• Comparing only adjacent marked cells: The entire extra area is a common unit.
• Guess too early: Several remaining candidates are not yet a reason for guessing.
• Not rechecking after an entry: A single value can simultaneously change multiple units and clues.

Tips for Beginners

• Start with units or clues that have especially much visible information.
• Write down small sets of candidates instead of mixing possibilities mentally.
• Always check a candidate against each rule affecting its cell.
• Treat confirmed exclusions as real progress, even if no value is set yet.
• If no move is visible, consciously switch from rows to columns, areas, and clues.

Girandola Sudoku becomes clear as soon as normal units and additional clues are consistently re-evaluated after each confirmed step. Small, fully justified deductions lead more reliably to the goal than early guessing.