Rainbow.js is compiling with the Closure Compiler's advanced mode now! The REPL page--which still doesn't load arc.arc--is now down to 146 KB (HTML and JavaScript), rather than over 500.
Furthermore, on most recent browsers, the loading speed seems competitive with, or even better than, the loading speed of Java Rainbow. It might not be a fair comparison, since the contents being loaded are coming through a different kind of input, but I'm still pretty excited. ^_^
