I learned this from Zed Shaw's Learn X The Hard Way books. He says this approach is mainstream in other disciplines, like music, languages, or martial arts. I

I learned this from Zed Shaw's Learn X The Hard Way books. He says this approach is mainstream in other disciplines, like music, languages, or martial arts. I also heard the philosopher Ken Wilber spent a few years (in what kids today call Monk Mode) writing out great books by hand. The main effect I noticed is that I rapidly gain muscle memory in a new programming language, library or codebase. The other effect is that I'm forced to round-trip every token through my brain, which is very helpful as my eyes tend to glaze over — often I'll be looking right at an obvious bug without seeing it.