A walkthrough would be nice, but he's got a lot of understandable material linked on that page. For example, here's an overview of the binary lambda calculus: https://tromp.github.io/cl/Binary_lambda_calculus.html

And here's a readable and fascinating post on "the largest number that's representable in 64 bits": https://tromp.github.io/blog/2023/11/24/largest-number.

If you go through these and find some interesting things, it'd be worth posting to HN.