△ Geometry

From Euclid to curvature. Runnable code, SVG diagrams, plain English.

	Chapter
1.	Euclidean Geometry	Five axioms, compass and straightedge, and the theorem that launched a thousand proofs	△
2.	Coordinate Geometry	Descartes put numbers on geometry: distance, slope, lines, and conic sections	△
3.	Transformations	Translate, rotate, reflect, scale — and discover that symmetries form a group	△
4.	Projective Geometry	Add points at infinity so parallel lines meet, then watch points and lines swap roles	△
5.	Non-Euclidean Geometry	Drop the parallel postulate: on a saddle there are many parallels, on a sphere there are none	△
6.	Differential Geometry	Curves bend, surfaces curve, and curvature is a number you can compute	△
7.	Metric Spaces	Distance functions, open balls, and metric spaces as enriched categories	△
8.	Convex Geometry	Convex sets, convex hulls, separation theorems, and Minkowski sums	△
9.	Voronoi Diagrams	Nearest-neighbor partitions, Voronoi cells, and Fortune's algorithm	△
10.	Delaunay Triangulation	Dual of Voronoi, circumcircle property, convex hull in one higher dimension	△
11.	Power Diagrams	Weighted Voronoi diagrams and the geometry behind ad auctions	△
12.	The Erlangen Program	Klein's insight: a geometry is defined by its symmetry group	△

Neighbors

📐 Linear Algebra — dot products, projections, and transformations are geometric
∫ Calculus — differential geometry uses multivariable calculus
∞ Real Analysis — metric spaces generalize geometry
⚙ Algorithms — Voronoi diagrams and Delaunay triangulation are computational geometry