Demotive is built using Jekyll with a couple of plugins
It’s then popped up to Gitlab, and upon each merge to main a thingummy publishes the site to render.com
Serif type is IBM Plex Serif
Body type is -apple-system, system-ui, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif; - so you’ll probably be seeing something like Segoe on Windows, San Francisco on macOS, and Roboto on Android.