Mathematics is the science of patterns — and the closest thing we have to magic that actually works. It lives entirely in your head, needs no batteries, and gives answers you can be certain about. Best of all, once you prove something is true, it stays true forever: the rule Pythagoras spotted about triangles 2,500 years ago is still exactly right today, and always will be.

The toolkit everything else borrows

Here's the sneaky part: maths is the toolkit every other subject reaches for. Physics writes the laws of the universe as equations; computer science is, underneath it all, just maths you can run on a machine. Learn maths and you've quietly picked the lock on both — which is why it's the trunk this whole tree of knowledge grows from.

Where to climb in

Every branch of maths grows from a few simple ideas you already half-know. Start with Arithmetic — counting, adding, and the patterns hiding inside ordinary numbers — then work your way up to Calculus, the mathematics of change and motion. Each page names the ideas it builds on, so you're never lost: just keep following the branches upward.