Every answer shows its working
We never publish a bare answer. Each worked example states the assumption, the steps and a test of where the result stops holding.
Our principles
Explain the reasoning, credit the source
Brain Picnic Frnzy is an independent educational site for curious adults and older students. We are not affiliated with any puzzle publisher, game federation or gambling operator.
Traditions are named precisely
We attribute puzzles to specific places, periods, people and texts — Sunzi, Yoshida Mitsuyoshi, Bhaskara II, Choi Seok-jeong — rather than to a vague "Asia".
Uncertainty is stated
Where dates or origins are disputed, we say so. Legends are labelled as legends, and documented history as documented.
Accessible by design
Diagrams have text equivalents, notation is written as readable HTML, and nothing relies on colour alone.
How we work
Our editors check each mathematical claim by working it independently, and check historical claims against published scholarship such as museum catalogues, university press histories and translated primary sources. Images are illustrative 3D renders of counters, tiles and geometric objects; when a diagram matters to the mathematics, we draw it accurately or describe it in words.
Corrections
If you find an error, tell us. We correct the page, note what changed, and thank readers who agree to be named.
Probability material on this site is educational. It is not betting advice, and no reasoning method overcomes the built-in house edge of commercial games of chance.