sounds amazing. Your tool is super useful for understanding recursive functions. Only thing I felt that I was missing when using this was a format button to fix the formatting of my code.
Thank you for your feedback! I believe it has some value in teaching programming in the spirit of "Structure and Interpretation of Computer Programs." There is a JavaScript edition of the SICP book. I believe Leporello.js would be a nice environment for students to solve problems from this book.