Bit-Shadow Machine renders particles in a web browser using CSS box-shadows. That's it. No HTML5 Canvas, WebGL or even a single DOM element. Check out the examples below or get more detail from the repo.
By default, the box-shadows are attached to your document's body. Freed from parsing the render tree, the browser can animate many more particles than with conventional methods. You can easily render several hundred particles at 60 frames per second.
Box-shadows also have a blur property which allows us to render a motion blur effect! Pretty cool considering we're just moving around CSS box-shadows.
You can also organize your pixel particles into "frames" and animate big blocky-style pixel art.
Here's the opening scene to a longer animation about a little box of milk who runs away from home.