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Calcdoku puzzles don't allow repeat digits in any row or column, but repeats can happen in differently shaped regions. Can you repeat any digits in the center cross of this puzzle?

Someone removed ornaments from your mobile and rebalanced it with new ornaments. What are their weights?

When we know the area of one of a pair of similar figures, finding the other area can be easier when we relate lengths instead of using area formulas. Find the area of the lune.

In some games, it's possible to play perfectly. What choice guarantees a win in this game?

Adding a mirrored barricade to a reflection box introduces a new angle to this ray-tracing challenge.

Finding the longest possible path between vertices in a network can come down to counting the lines from each vertex. There's an additional wrinkle in this problem, since some paths are straight while others are curved.

With operator search puzzles, you can change the +, -, ×, and ÷ symbols of an equation. Think about how even and odd numbers combine by these operations when solving this puzzle.

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