Higher dimensions, made visual
The math past single-variable calculus, drawn instead of memorized: vectors, matrices as motions of the plane, the directions that refuse to turn, surfaces you can walk on — and the eigenvalue test that tells a summit from a mountain pass.
Module 1 · Vectors & space
Module 2 · Linear transformations
Module 3 · Eigenvectors & eigenvalues
Module 4 · Surfaces & partial derivatives
Module 5 · Optimization in two variables