What Is Shikaku? Rules, Examples, and Solving Tips
Summary:
Shikaku is a logic puzzle where the goal is to divide a grid into rectangles that match the clues provided. This guide explains the rules of traditional number-based Shikaku puzzles and the patch-based variation available in Puzzle Maker Pro.
What Is a Shikaku Puzzle?
Shikaku is a Japanese logic puzzle in which a rectangular grid must be divided into non-overlapping rectangles.
Each rectangle must:
- Contain exactly one clue.
- Match the clue associated with that rectangle.
- Not overlap any other rectangle.
- Completely cover the puzzle grid.
The challenge comes from determining how the rectangles fit together using logic rather than guessing.
Traditional Shikaku Rules
In a traditional Shikaku puzzle, each clue is a number.
That number represents the area of the rectangle containing the clue.
For example:
- A clue of 4 must belong to a rectangle covering exactly 4 cells.
- A clue of 6 must belong to a rectangle covering exactly 6 cells.
- A clue of 12 must belong to a rectangle covering exactly 12 cells.
The rectangle can have different dimensions as long as the total area matches the clue.
For example, a clue of 12 could be:
- 3 × 4
- 2 × 6
- 1 × 12
The correct rectangle depends on the surrounding clues and available space.
Rules Checklist
When solving a Shikaku puzzle:
- Every rectangle must contain exactly one clue.
- The area of the rectangle must match the clue.
- Rectangles cannot overlap.
- Rectangles cannot leave gaps.
- The entire grid must be filled.
If any of these rules are broken, the solution is incorrect.
Basic Solving Strategy
Start with Large Numbers
Large clues often have fewer possible placements.
These clues can help establish the overall structure of the puzzle.
Look for Forced Shapes
Some clues can only fit one rectangle shape because of nearby clues or grid boundaries.
When this happens, fill in those rectangles first.
Eliminate Impossible Placements
As rectangles are identified, they reduce the available space for other clues.
This often reveals new forced moves.
Complete the Grid
Continue using deduction until every cell belongs to exactly one rectangle.
What Are Patches?
Puzzle Maker Pro includes an alternative puzzle style called Patches.
Instead of displaying numbers, the puzzle uses visual clue symbols.
The puzzle is still solved by dividing the grid into rectangles, but the clues provide shape information rather than area values.
Patch Types
Square
A square patch indicates that the hidden rectangle is a square region.
Examples:
- 2 × 2
- 3 × 3
- 4 × 4
Horizontal
A horizontal patch indicates a rectangle that is wider than it is tall.
Examples:
- 2 × 4
- 2 × 5
- 3 × 6
Vertical
A vertical patch indicates a rectangle that is taller than it is wide.
Examples:
- 4 × 2
- 5 × 2
- 6 × 3
Mixed (Either)
Mixed hints provide less information.
The rectangle may be square, horizontal, or vertical.
These clues increase puzzle difficulty because they give the solver fewer restrictions.
Number Puzzles vs Patch Puzzles
Number-Based Shikaku
Benefits:
- Traditional puzzle style
- Familiar to many logic puzzle fans
- Direct clue information
Patch-Based Shikaku
Benefits:
- Visually distinctive
- Different solving experience
- Useful for themed puzzle books
- Supports custom patch images in Puzzle Maker Pro
Both puzzle types use the same core rectangle-placement logic.
Shikaku Solving Tips
- Start with the most restrictive clues.
- Use grid boundaries to eliminate possibilities.
- Check that every rectangle contains only one clue.
- Look for cells that can belong to only one region.
- Revisit earlier assumptions when new rectangles are confirmed.
- Work systematically rather than guessing.
Learn How to Create Shikaku Puzzles
Interested in creating your own Shikaku puzzles?
Puzzle Maker Pro – Shikaku can generate both traditional number puzzles and patch-based puzzle variations.
Product Page: https://www.bookpublishertools.com/product/puzzle-maker-pro-shikaku
Related Resources
- Shikaku Tutorials:
https://www.bookpublishertools.com/shikaku-tutorials/