🔲 Kakurasu

A logic puzzle with weights (numbers) assigned to columns and rows. Figure out the pattern so the sum of the column numbers for filled cells matches the hint on the right, and the sum of row numbers matches the hint at the bottom!

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Puzzle Solved!

way of playing (a game)

  • Each column in the grid has a weight (column number) from 1 to 7.
  • Right hint number = sum of column numbers for filled cells in that row
  • Bottom hint number = sum of row numbers for filled cells in that column
  • Click to fill a cell black / Click again to return it to white
  • Right-click (or double-tap) to toggle pencil marks
  • Auto-check when all cells are filled. You can also check mid-solve with the "Check" button.

What is Kakurasu?

Kakurasu is a number-placement logic puzzle combining Sudoku's constraint logic with crossword-style clues. Each cell contains either a digit (1-9) or remains empty, and row/column clues specify the sum of numbers in that line and how many cells must be filled. Using pure logical deduction, you determine which cells stay empty and which contain specific numbers to satisfy all constraints.

How to Use

Read the column and row clues indicating the required sum and cell count for each line. Start with clues having limited solutions and deduce outward systematically. Mark cells as filled or empty, placing numbers logically. If a row must sum to exactly 10 with one filled cell, that cell must be 10. Progress through logical elimination steps until the entire grid satisfies all constraints simultaneously. Save progress to resume later.

Use Cases

• Logic puzzle enthusiasts enjoy the constraint-satisfaction challenge requiring pure deduction skills
• Computer science students study Kakurasu as an NP-complete problem exemplifying algorithmic complexity
• Casual puzzle fans solve medium-difficulty variants during commutes for mental stimulation
• Educational settings teach problem-solving strategies through guided progressions from simple to complex variants

Tips & Insights

Start with easiest puzzles to understand mechanics, then progress to harder variants systematically. Clues with unique sums limit possibilities dramatically—prioritize these first for maximum deduction. Unlike Sudoku, empty cells create additional logical branches requiring different thinking approaches. Writing candidate numbers in cells helps track possibilities visually before committing to final answers.

Frequently Asked Questions

What are the rules of Kakurasu?

Each column is assigned a weight from 1 to 7. The hint number on the right of a row is the sum of the column numbers for filled squares in that row. The hint number at the bottom of a column is the sum of the row numbers for filled squares in that column. The puzzle is solved when all row and column hints match their sums.

What is the pencil memo feature?

Right-click (or long-tap) to mark a square with a pencil. By marking candidate squares you've ruled out, you can better organize your solving strategy.

How do you know if you've made an error?

When the grid is completely filled, it's automatically checked. You can also verify your work at any time by clicking the 'Check' button, and incorrect row and column hints are highlighted in red.

How many types of puzzles are available?

7 different 7×7 grid puzzles are included. Switch between them in order with the "Next Puzzle" button.

What's the difficulty system for Kakurasu puzzles?

Puzzles range from Easy to Hard, with difficulty increasing based on the grid size and the logical deduction needed to solve them. Larger grids and more complex number combinations require deeper strategic thinking. Start with Easy if you're new to Kakurasu, then progress to harder puzzles as you get comfortable with the logic.

Can I undo my moves if I make a mistake?

Yes, most implementations include an undo button or use Ctrl+Z to revert your last move. This lets you experiment without losing progress. Additionally, the error-checking feature will alert you if a move violates the puzzle rules, helping you correct mistakes before they cascade.

How long does it take to solve an average puzzle?

Easy puzzles typically take 5-10 minutes, medium puzzles take 15-25 minutes, and hard puzzles can take 30+ minutes depending on your experience level. The satisfaction comes from steady logical deduction rather than speed. Remember, the goal is to enjoy the puzzle-solving process, not race against the clock.

Is there a hint system if I get stuck?

While the tool may provide error feedback, explicit hints aren't typically built-in to the core game. Instead, re-examine which clues you haven't fully used yet or look for cells where only one number can logically fit. Taking a break and returning with fresh eyes often helps solve that stubborn area.

Can I print Kakurasu puzzles to solve on paper?

Yes, you can use your browser's print function to save or print the puzzle. This allows you to solve offline or prefer pen-and-paper solving. Just note that interactive features like the pencil memo won't work on printed versions, but the puzzle grid and clues will display clearly.

What should I do if I'm completely stuck on a puzzle?

First, verify all your current entries are correct using the error-checking feature. Then, look for rows or columns where the clue number is very small or large—these often have fewer possibilities. If you're still stuck, try a different puzzle and come back later, as fresh perspective is often the key to breaking through.