Welcome to the Functions Series, the hands-on companion to the Inference Series. Where the inference series established that a deterministic function can play the CxPU role as cleanly as an LLM can, this series teaches you to actually build them — in your own vocabulary, without writing code. You describe what the function should do in the words you naturally use to think about your domain. The IDE produces the implementation and explains it back to you in the same vocabulary, so you can verify it matches what you intended and refine it until it does. The implementation is real software — imperative C compiled to WebAssembly, deployable as a static-inference CxPU — but you never see it unless you choose to. The architectural pattern that makes this possible is called dynamic domain targeted decompilation, and the series will teach you to use it as a co-author rather than as a customer of someone else's tool. No prior programming experience is required. What you bring is your domain expertise. The series shows you how to use it to build software.