Guides
Categories tell you what a tool does and collections tell you who it is for. These answer the question that comes before both: what are you actually trying to do, and which approach fits? Each one leads with the decision — the arithmetic, the trade-off, the ceiling — and points at tools as the answer rather than as the subject.
- Choosing a tournament formatKnockout, round-robin, Swiss, double elimination, ladder or boxes — what each costs in time and what each guarantees.6 sections · reviewed 2026-10-09
- Running a prize draw people will believeA draw being fair and a draw looking fair are different problems. How to solve the second one without pretending you have solved it.5 sections · reviewed 2026-10-09
- Splitting a group fairlyTeams, pairs, rotations or a constraint solver — what 'fair' means in each case, and the ceilings a shuffle cannot get past.5 sections · reviewed 2026-10-09
- Proving a draw was fairWhat a seed actually gives you, why the order you publish it in decides everything, and where reproducibility is the wrong tool.5 sections · reviewed 2026-10-09
- Why coincidences are likelier than they lookTwenty-three people, a shared birthday, and why the same arithmetic decides how many random codes you can safely issue.4 sections · reviewed 2026-10-09
- Setting up a gift exchange that can actually be drawnExclusions, households and no-repeat rules interact, and a hat cannot tell you when they have made a draw impossible.4 sections · reviewed 2026-10-09