codecrafters-io/build-your-own-x

This repository is a curated index of step-by-step guides for re-creating well-known technologies from scratch. The philosophy is captured by a Richard Feynman line printed near the top of the README: "What I cannot create, I do not understand." The idea is that you learn a technology most deeply by trying to rebuild it yourself rather than only reading about it. The README organizes the material as a long table of contents. Categories include 3D renderers, AI models, augmented reality, BitTorrent clients, blockchains and cryptocurrencies, bots, command-line tools, databases, distributed systems, Docker, emulators and virtual machines, front-end frameworks, games, Git, memory allocators, network stacks, neural networks, operating systems, physics engines, processors, programming languages, regex engines, search engines, shells, template engines, text editors, visual recognition systems, voxel engines, web browsers, and web servers, plus an uncategorized bucket at the end. Each category links out to external tutorials, blog posts, and books that walk through implementing that technology. Every entry is tagged by the programming language it uses, for example C++, Python, Go, Java, JavaScript, Ruby, Kotlin, Scala, Crystal, Nim, or TypeScript. A single category often spans many languages, so a reader can usually find a tutorial in the language they already know. You would use this collection when you want to move past tutorials that mostly wire pre-built libraries together, and instead see how a database, a Git clone, a tiny blockchain, or a small operating system is actually constructed under the hood. Because the resource is itself a list of pointers to other people's writing, the project is in effect a curated awesome-list (one of the repo's own tagged topics) written in Markdown, not runnable code that you clone and execute.