The animations for Spinning Numbers are created with the Javascript library D3.js. The source code for animations is here.

I also use D3.js to create static graphs and calculated waveforms. The source code for static graphs is here. I open each d3 html file, touch up annotations here and there, and save the resulting svg image to the i/ folder.

I found this handy Chrome-specific bookmarklet, SVG Crowbar. It extracts the svg images from a web page and presents it in a form that can be saved as an svg file.

Euler’s sine wave

Euler’s cosine wave

Euler’s sine and cosine