Building out your vision is a fluid thing. It morphs. It evolves. You f*** up. What have you. Whatever you start with is not going to be what the end product looks like at any point of this venture. But start you must. Remain loose, you must. Get ready to iterate. Accept it. Do your best. Continue marching. One day, you'll have a masterpiece on your hands. And you'll then probably have to start over all again, in some way. It is the way of these things.