Monty Hall with N doors
Move the door count and the number of doors the host opens. The model puts the advantage of switching at (N−1)/R — it tracks the reveals, not the door count.
0.667the model's switch win rate at three doors
Interactive workbench
Move the number and see what happens.
A textbook gives you one equation and one answer. Here you get the dial.
I make small tools for questions where the arithmetic is short and the answer still feels wrong. You drag a slider, a chart moves, and you can watch the point where your intuition gives out.
Being told that switching doors wins two games in three convinces almost nobody. Watching ten thousand simulated games settle onto 0.667 is a different experience. That is the whole idea.
Chance
Probability, queues and pooled averages — short arithmetic, and an answer you want to argue with.
Scale
Orders of magnitude, and the axis you draw them on. What a number does when the exponent moves.
Motion
Vehicles, mechanics and the arithmetic of getting somewhere — each formula drawn with the range where it holds.
Energy
Power, heat, water and fuel — what a habit actually costs once the two halves of the bill are drawn apart.
Every tool has a written page under it: what the model assumes, and what it leaves out. I add them when they are finished, not on a schedule.