This page is made using svelte-fullpage component, try to scroll, drag with mouse or swipe vertical with finger or use arrows to scroll.
There is also component for slides as you can see. Try to drag/swipe right or left, also you can use arrows.
You can style every individual slide, notice background change.
svelte-fullpage supports also embeds and iframes, scroll down to see example, you will see page but loaded using embed. Scrolling on embaded page is enabled, but also fulpage scrolling is still working, try to scroll hovering over fullpage section indicator (grey dots).
This component is in development and is far from being ideal, as you noticed (maybe), there is problem with slide animation. Currently I'm the only contributor of this project, feel free to fork it and make pull request.