This looks very interesting, particularly the visualization tool. One thing I think it sheds light on is the difference between a simple library and a framewor

This looks very interesting, particularly the visualization tool. One thing I think it sheds light on is the difference between a simple library and a framework. Many frameworks can be thought of as providing an interpreter that you configure using callbacks. Debugging a high-level program by stepping through the interpreter that's executing it isn't easy. Custom debugging tools make it easier.