Each lesson is built around a single big idea — the kind that, once you see it, changes how problems feel forever. They start at primary-school level and end at the edge of algebra. Read, draw, then try the practice problems at the bottom of each lesson.
Lesson 04 — in progress

Coming soon…

Ideas in the queue: fractions on a number line, the four laws of arithmetic visualised, place-value bars, area models for multiplication, "Why does long division work?" Tell me which one to build first.