When first learning a programming language it is nice to see the code executed step by step. Many of us use gtrace/0 with SWI-Prolog but that is typically putting the cart before the horse in that you have to have a basic knowledge of Prolog, consulting code, calling predicates, etc. What would be nice is to just click on something and watch the code execute.
GitHub repository: cdglabs/ prolog-viz
Slides