I had a tough time getting the masonry layout to work well. Libraries didn't quite do the design justice, nor did various CSS Grid-based workarounds. There were a couple of other CSS-only solutions that could maybe have worked, but felt hackier than what I ended up with. The main problem with my solution is tab order--it goes down each column rather than left-right through the "rows".
Getting the transitions to run correctly when moving forward/backward through the "slides" was a challenge, but overall, working with animations/transitions in Svelte is really nice.
The site is prerendered and (I think) totally usable without JavaScript enabled