1. The spark : Spaceships, combat and inertia.
A finished game is something solid, clear and detailed. The rules are precise, victory conditions are well defined, as are the means to reach them. In the beginning however, things are much more murky. There is nothing, or almost nothing. A spark, a blurry aspiration to something.
One morning I was toying around with the idea of a low complexity space combat. One ship per player, simple actions : move forward, turn, shoot, … and we merrily duke it out. I already created such a game, with simultaneous programming followed by a common resolution of the moves. Here I rather thought about turn-based, where you would end your turn by secretly choosing your next turn's move.