This is made with (and by the author of) <css-doodle>, a web component that lets you put the CSS variant used in this blog inline into your HTML, like so:

    <script src="https://esm.sh/css-doodle/css-doodle.min.js?raw"></script>
    <css-doodle>
      @grid: 15 / 90%;
      border-radius: 50%;
      background: hsl(@t(/20), 70%, 60%);
      scale: sin(@atan2(@dx, @dy) + @ts);
    </css-doodle>

No JS needed except for loading the definition of the <css-doodle> component. Works in plain HTML, Markdown, frameworks, etc.

https://css-doodle.com/