Do you love watching videos about esoteric languages and have daydreamed about writing your own? Have you given up on the status quo of programming languages and decided to fix it yourself? Are you the kind of kid who’d ask about the semantics of a new operator in math class and are wondering how it all works? This class should give you the tools to do just that! In this tutorial, we’ll implement the simply typed lambda calculus, the foundation of all programming language theory, from only a parsing library in one sitting. We’ll discuss the theory of syntax, evaluation, and type checking while staying rooted in representation and the user experience. Students will collaborate with lecturers to develop core parts of the language, and should ultimately walk away with the knowledge to hack on the language built in class or build their own.