Cool project, I had been using markdown based slide tools for similar use-cases:

- Marp: https://marp.app/

- Slidev: https://sli.dev/

- Revealjs: https://revealjs.com/

Something more similar, based on HTML and CSS but instead based on the Svelte framework, was Animation: https://animotion.pages.dev/

It focuses on presentations that include animations, but of course it's flexible.