The use of external modules…

…is highly encouraged. Split code into external modules, but not too many otherwise you will reduce your own thought flow as you flick back and to between them. And reducing thought flow leads to reduced code flow. Be logical, be consistent in what you put external to the main core. The core should be as small as possible, but not at the sake of clarity. If a particular piece of code doesn’t get used very often then make it external to the core. If it get’s used a lot, but it’s function is highly abstract or hard to visualise then make it external to the core. Only keep code in the code when it’s necessary, and when it enhances flow by making the core into 1 easy to read and understand module.