Field
What makes it checkable
A seeded generator, so a figure is the same on every build. A closed form beside every simulation, so there are two routes to each number. And p-values checked for uniformity, which catches errors no rejection rate would reveal.
The seed is part of the figure
Every other site in this fleet draws from a deterministic rule, so a figure either is or is not what it claims. Here the figures are samples, and a sample can be right by luck. That changes what a figure has to carry.
Two routes to every number
A site about probability that only simulates has one route to each answer and no way to tell a right one from a plausible one. Every important number here is computed twice, by arithmetic that shares nothing, and the two are required to agree.