Thank you! Really sorry about the lag. We have a bunch of shader code, particles, and some models have quite a few total polygons for what they are.
We're looking to improve by preloading, quickly rendering in-front of a camera, and caching some particles or shader resources. Or, whatever it takes, this is a new problem for us using Godot. The lag wasn't a problem in the debug builds from editor :(
I removed the HTML build for the meantime. The consistent lag and bad loading were far too distracting. We'll try to release v0.1.1 soon.