Earlier quoted context omitted.
> Simple code won't usually handle complex stuff I think you are confused about what simple code means.
Enlighten me with your definitive and universal definition of simple code then :-) (but I'm totally happy with isoprophlex's answer actually)
Most any software can be broken down in a modular way so that the units could be understood by a junior and you'd rarely need to think about more than one cluster of interactions at once. Maybe this is naive, but up until now found it to be true - that said, I never worked in rocket science.