For the prototype I just created one area with two npcs and one item to be picked up. I focused on showing how the player can make choices which alter the course of the game by changing things depending on what npc the one item is given to (this is based on the feedback I got saying how cool it would be for the game to not be straightforward but for you to have choices like that). I just started working in Bitsy right away because it is simple to drag things in. What I did is basically the equivalent of gray boxing. It is work in the engine I'm using but none of the visuals are final.