what is crustacean fr?

Crustacean is a free, interactive learning platform that teaches you the Rust programming language. It walks you from complete beginner to advanced topics like memory management and code generation, using bite-sized lessons you can work through right in your browser. You can use it online or run it on your own machine to learn offline. The app runs entirely in your web browser, so you can read a concept and immediately practice it with built-in coding exercises. It includes a command palette and keyboard shortcuts designed to keep your hands on the keyboard while you navigate lessons and run code. Instead of using a traditional compiler to check your exercise answers, it uses a lightweight matching approach to validate that your code meets the lesson requirements. This project is built for anyone who wants to learn Rust interactively, whether you are a developer tackling the language for the first time or an experienced programmer wanting to master advanced topics. It is also designed for educators and creators who want to build custom courses. Using an AI assistant, you can generate an entirely new Rust curriculum in minutes by pointing the AI to a specific instruction file, having it create the lessons, and then registering the new course in the platform. One notable design choice is how the project handles course creation and validation. Rather than relying on a traditional backend compiler, the platform uses a "frontend-only" philosophy where exercises are checked using custom matching rules. This keeps the app lightweight and client-side. Under the hood, it is built with a Rust web framework and styled with standard tools, then deployed as a containerized application that updates automatically whenever changes are pushed to the main branch.