OXY

A small language for geometry. You write how a figure is built — its points, lines and circles, where they cross, how they turn and reflect — and then drag the given points to see the construction hold. It runs in the browser; there is nothing to install.

Open OXY — it starts on Euclid's first proposition.

Books

All 48 propositions of Book I of Euclid's Elements, each a script that builds the figure one step at a time, saying at each step what Euclid says, with the given points ringed so you can drag them. Beside them, the chapter on the circle from A. P. Kiselev's Elementary Geometry, translated from the 1914 edition: the text on one side, its constructions live on the other. And lessons from the OXY kit of 1994: finding the best point on a line or for five houses by trying, then seeing why it is there, and two reflections or two turns that make a single turn.

Language

A page for each thing OXY has that other programming languages do not: figures and their numbered and named points, moving whole figures, finding where lines meet, the nearest point or whether a point is inside, points to drag and numbers to set, steps, angle marks, fills, stroke fonts and points with formulas.

Fun

Animations, trails and fractals in a few lines each: a solar system, a rolling wheel, a spirograph, the Koch snowflake, Sierpiński's triangle, a fractal tree, and three demos from 1994 with letters that wave and turn. Every one is open to edit; change a number and run it again.

Your own scripts

Write your own under My scripts. They are kept in your browser as you type, and you can download a script or open one from your computer. SAVE and LOAD keep figures in files, and FONT draws text in stroke fonts — the Hershey fonts come with OXY, Russian letters included — whose letters are segments like any other, to turn, reflect and press. The Help beside the script is the whole language reference.

Gallery

Euclid's Elements, I.1Kiselev's Geometry: the inscribed angleTimes tables on a circleThe Koch snowflakeLetters are figuresOn a phone

From the early 1990s

OXY began in 1991–92 as Oxygen, a Turbo Pascal program for MS-DOS. This is a new implementation of the language as it stood in 1995, in Swift, compiled to WebAssembly so it runs in the browser; the scripts written for that version still run. Some things are new: points the reader drags, colors by name, the books.

Privacy

OXY needs no account and sends nothing anywhere: your scripts and files stay in your browser's storage, on your device. Clearing the site's data removes them, so download the ones you want to keep.