It's frustrating that your link to an "explanation" is an intentionally buggy implementation of the algorithm :(

I understand the point of the debugging game, but in this context, a link to the solutions page would be more helpful....

Replace

  at = root

with

  at = next[root]

and you're done. Once you understand the forward transform, you understand that root is the LAST byte and next[root] is the FIRST byte.

All the fixes in BUGFIX-66 are trivial if you understand what the code is doing, that's part of the game concept. Also, if you submit broken code, it gives you a useful hint to direct your attention to the bug.

Similarly, the fix for the forward transform is to add

  i1, i2 = x[i1], x[i2]

at the top of the less() function.

> Wikipedia gives an impractical, inefficient account of the algorithm. It's almost comically bad.

I encourage you to edit and fix it.

I love your site! Hope you don't mind that I sent you an email.

It's a fantastic example of minimal yet fully functional!

Thanks. I just recently started building it.

Understanding small, elegant algorithms (enough to make tiny fixes) is something I consider fun. Hopefully it's fun for others.

Imagine the book Hacker's Delight, but turned into a simple debugging game. That's the concept.