Pretty neat idea, but it evaluates the lzcnt instruction incorrectly, so it's possible others are wrong too. If you have access to a real x86_64 processor, you're probably better off just using it, and then you get the power of a full debugger with breakpoints in gdb.
Also, the "Guides" button and the "embed on your website" link on the main page are broken.
Also, the "Guides" button and the "embed on your website" link on the main page are broken.