So maybe you have an idea but you’re not really sure whether to develop it or not. How would you know? Well how about:
Do your thoughts keep drifting back to it?
Do you find yourself carrying around a notebook and scribbling half-imagined thoughts at inappropriate times?
Are you obsessing on particular parts of it just for fun?
These kinds of behaviours are what passion looks like. They’re the point where game making is not just an intellectual exercise or a problem to be solved, but instead where you’re excited. The most important question to ask is this:
Would you play it?