Build Your Own X

Codecrafters is an online platform offering advanced programming challenges for experienced engineers. It provides guided projects to rebuild real production tools (for example Redis, Git, and SQLite) from scratch inside the user's IDE.

CS-Books is a maintained GitHub resource repository collecting computer-science books, study notes, articles, interview materials, and related learning links. It covers C and C++, Java, Python, Go, algorithms and data structures, operating systems, Linux, backend architecture, computer systems, networking, databases, frontend development, machine learning, deep learning, NLP, design patterns, assembly, Git, mathematics, and programmer skills. The repository organizes the materials by subject and states that it is updated gradually by its maintainer; its README also says that many links were collected from other online sources and invites reports of potentially infringing material for removal.

gstack is an open-source skill and tooling framework for Claude Code, developed by Garry Tan. It turns Claude Code into a virtual engineering team through Markdown-based slash commands and specialist roles covering product review, engineering management, design review, code review, browser-based QA, security auditing, release management, documentation, and other software-delivery tasks. Its tools can drive a real browser and support unit-test, end-to-end-test, and black-box verification loops. The repository describes 23 specialist tools and eight power tools, and distributes the project under the MIT license. It requires Claude Code, Git, and Bun; Node.js is additionally required on Windows.

Shell Gym is an interactive Linux command-line trainer implemented as a background daemon with a built-in web UI. It presents short assignments, or “reps,” such as entering a directory, creating a file, killing a process, or freeing a port; the assignment completes automatically when the corresponding system state changes. Users type real commands in an ordinary terminal while the UI observes the host and provides guidance, without modifying the shell or using prompt hooks, wrappers, special functions, a check button, or copy-and-paste. Its outside-the-shell observation uses procfs to discover interactive shells and inspect working directories, processes, files, and ports; the Linux kernel proc connector to observe exec() events; and direct state checks for files, processes, and listening ports. It runs on a Linux host as root, with an online playground also available, and the project advises using a disposable VM or other disposable Linux system because exercises perform real actions on the live host.

An open-source reconstruction of the historically lost B programming-language compiler, developed by Angelo Papenhoff. Its B implementation uses two phases: `bc.b` compiles B source into an intermediate format, and `ba.b` converts that format into assembly; the first phase is mostly platform-independent apart from word size, while the second is platform-dependent. The repository also contains an initial C compiler used to bootstrap the B compiler, capable of producing PDP-11, amd64, MIPS32, and RISC-V 64 assembly, plus reconstructed variants for UNIX v1 on the PDP-11 and ITS on the PDP-10. The compilers generate the original threaded code, with the PDP-10 version using ASCII intermediate code. The project has been confirmed to compile itself on Linux amd64, Linux MIPS32, Linux RISC-V 64, 2.11BSD PDP-11, UNIX v1 PDP-11, and ITS PDP-10.