Hi! Author here. I just used the Canvas API with some vanilla JavaScript code. My site is built with Hugo, so I first needed to create a shortcode that allows me to embed .js files I created for simulations directly into my posts. About the code for animations being shown, I didn't write them myself from scratch. I used LLMs to generate them. They are not as accurate as what I had in my mind, but it still worked out fine after some iterations and improved the overall reading experience I believe.