I quickly took the most classic puzzle book of the series to heart. Although the puzzles are solved in a similar way to Sudoku, they required me to think outside the box and didn't result in repetitive work.
★★★★☆ Andreas Giesbert (Zauberwelten-Online)
Cold Hearts is an original number puzzle that combines logic, deduction, and a touch of math.
- 300 Puzzles.
- Easy and medium difficulty.
- Unique puzzle type.
- Solutions are included in the back of the book.
The goal is simple: fill the circles with the numbers 0–9, using each number only once. The numbers already placed outside the circles give you the crucial clues—they represent the sums of the numbers in the connected circles.
Each puzzle starts with one or two hints, but from there, it’s up to you to reason, calculate, and eliminate possibilities until every circle is filled. Easy to learn yet tricky to master, Cold Hearts delivers that satisfying “aha!” moment with every solution.
Perfect for fans of Sudoku, Kakuro, and other number-based challenges, Cold Hearts is both fun and brain-boosting—training logic, focus, and problem-solving skills while keeping your mind sharp.
Logic Lucy books can be bought on Amazon.
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