Wonderful Resources

Animated Times Table Circle (Modular Arithmetic Joy)

Diffusion Simulator - Click to Draw

Ulam Prime Spiral (Enjoy Looking for Diagonal Patterns of Primes)

Monte Carlo π Estimator

Why this works is straightforward! The unit circle has area π(1)^2 = π, so for a 2x2 square with an inscribed circle, out of 4 randomly placed dots, we expect pi of them are in the circle! The ratio is preserved regardless of group scale!

Pascal's Triangle Generator - The left and right sides are all 1, you get the lower number by adding the 2 above, only odd numbers are highlighted!