Product notes
Product updates, new challenges, and improvements, newest first.
Classes for Interpreter
Add classes, instances, constructors and methods to your Lox interpreter.
Resolving and Binding for Interpreter
Implement variable resolution and binding in your Lox interpreter.
Build a Shell in Gleam
The Shell challenge now supports Gleam.
Rust for Impatient Developers
Learn Rust through short, interactive lessons designed for experienced programmers, with saved progress and a mobile-friendly flow.
Command autocompletion for Shell
Add tab completion for commands and executable names to your shell.
Shell redirection
Redirect or append standard output and errors to files in your shell.
Faster CLI runs over slower connections
CLI test runs became faster on poor connections and farther from the test servers.
Shell quoting
Handle quoted strings, spaces and escaped characters in shell commands.
More challenges in PHP
PHP support expanded to Shell, Grep, Interpreter and Redis.
Interpreter: Functions
Add function definitions and calls to your interpreter.
Build Redis in Zig
The Redis challenge added Zig support.
Concept feedback without an account
Concepts began accepting feedback from anonymous learners.
Reading is good.
Doing is better.
Build your own Claude Code, Shell, or SQLite. Understand what’s underneath.