Don't be fooled by the paucity of lines, that Codepen is of course pulling in an entire JS file: https://unpkg.com/css-doodle@0.34.7/css-doodle.min.js https://u

Don't be fooled by the paucity of lines, that Codepen is of course pulling in an entire JS file: https://unpkg.com/css-doodle@0.34.7/css-doodle.min.js https://unpkg.com/css-doodle@0.34.7/css-doodle.min.js If you inspect what's getting rendered, there's a sprite map expressed as a data URI that's doing most of the heavy lifting.