Thanks!
I'd really like to know why things are much smoother on the native client. Is it just that the browser is less performant?
And yes we wanted to add the rule that 'encircling a trail would break it', but this would require adding spatial indexes to efficiently find subsections of trails, and we didn't have time to do that!
Consider that we got https://janhohenheim.itch.io/bike-game to run smoothly on Chrome at least, and that is a full 3D scene with lots of complicated geometry. With that in mind, I find it strange that you are running into performance issues. Maybe one of the underlying Bevy or Winit or wgpu APIs is somehow subtly broken on Wasm? I think the browser itself should definitely be performant enough for your use-case.