What is it?
What's the backstory?
What did I contribute?
For the sake of gameplay progression, the player needs to slowly discover the engine's code. So I had to create mechanics that give the player interesting ways of interacting with the code, and I had to create various techniques of "hiding" chunks of the engine code.
Also, I built into the code various kinds of "fail-safes" in order to avoid run-time errors and to roll-back certain changes.
In more recent versions, I've added sound effects that slow down / speed up as the game's time scale changes.