Internal Design
The runtime code consists of less than 100 lines of JavaScript bootstrap code and a few ActionScript classes. The ActionScript classes are compiled by jooc, and concatenated with the bootstrap code form the runtime scripts/jangaroo-runtime.js., resulting in a file of just about 32 kb (unzipped!). This approach is possible because the runtime ActionScript classes use only the most basic runtime features.
If during debugging, you have the impression there might be something wrong with the Jangaroo runtime or if you want to get a better understanding of its workings, you may want to try the runtime compiled in debug mode, which is available in the release and the corresponding Maven artefact as scripts/jangaroo-debug.js. Just reference this file instead of scripts/jangaroo-runtime.js in your HTML page, and you can do source-level debugging of the Jangaroo runtime.