In this book, we jump into a virtual machine, compiler and opcodes, without needing to read about parsing first. The language is already written, meaning you can dive into the source code of a working language right from the start (a programming language called langur, written in Go). Discover how to develop some very useful features, such as multi-variable assignment, decoupling assignment, string interpolation, short-circuiting operators, for loops, scoped if expressions, and more. We review how opcodes make these things work in a stack-based virtual machine.