My main area of technical focus is rapid prototyping (RP). That is, quickly generating game design products for the purpose of concept-proving, playtesting, and design iteration.
RP is a critical piece of the iterative design process. It means creating, as quickly as possible, a functional product that showcases and demonstrates important features of your game. The prototype is a functional expression of a game designer's intent. It's also used to evaluate key game mechanics in isolation.
A feature prototype exercises and showcases key features and mechanics in the context of your game in isolation, for example:
The prototype environment helps you tune, and iterate upon these features quickly, and helps you "find the fun".
My affinity for RP stems from much of my previous engineering work. I routinely built fuctional and interoperability test environments in short order. I used these environments to evaluate new hardware and features, such as: