The terrain information comes from data the Zelda modding community which was then smoothed and scaled down. It's Three.js with the lighting and shadows baked when the page loads.
I built it with Claude, as I did the timeline. Without it, I'd never have had the time for a project this whimsical, so it wouldn't have seen the light of day. I didn't write any of the code. For me it felt a lot like part of being a tech lead: shaping the ideas and the output.