and Hash Playground I'm the sort of person who gets very excited when simple rules create complex behaviour. The other day, I needed a simple hash function that maps $(x, y)$ coordinates to a colour, and found a straightforward equation that ended up being astoundingly rich. Hence this post; to talk about and play with this function. TL;DR: The boolean predicate $(c_x \, x + c_y \, y + c_{xy} \, x \, y + c_{x^2} \, x^2 + c_{y^2} \, y^2)$ $\mathrm{mod} \, m < \tau \, m$, is richly varied and beau...