Checkout this Arthur Whitney (Genius Language Designer/Programmer) thread - https://news.ycombinator.com/item?id=19481505
In the above thread, user "yiyus" actually went through the macro code line-by-line and made explanatory notes; unbelievable! - https://docs.google.com/document/d/1W83ME5JecI2hd5hAUqQ1BVF3...