workly.com
Proportion: Making a page, adding a drawing to it, and using "trace" to see the drawing.
To use Proportion.js, include the library, make a canvas on your page, and make your page run a JavaScript function on loading.

Once you have a Proportion Page object, add points, lines, and circles to it; then call "trace" to have your figure drawn onto the canvas.

Please look at the source code of this page for more information.