The separate visualizations are available: Factorial, reversing a string, and N-Queens.

Very nice visualizations for introducing the basics of recursion. Clear examples of the "stack frames" that get generated duing the recursive calls. Shows the sub-results of each recursive step.

Each of the three AVs presents appropriate information for its subject. The N-Queens is the most sophisticated of the three. For each, users enter a problem size (or sting for the string reversal). The visualization then either runs as an animation, or you can pause it and step through at your own pace (which is a much better idea until you have a pretty clear idea of what is happening).

There is a menu list on the left, click on "Algorithms" and from that page select the desired AV. These recursion AVs only have HTML5 (JavaScript) versions.