One of the greatest dangers that a game developer can ever face is to fall so in love with the aesthetics of their theme that they lose sight of ever actually making the game fun. World building may indeed be a wonderful creative exercise, but it is not a game.
Fixating too much on theme will often cause game developers to spend huge amounts of time and resources creating assets that may never even contribute in any meaningful way to the substance of the game. Many game projects have been ruined by this. It often causes game devs to fly blind for very long periods of time without ever testing whether their assumptions about how the game will end up feeling are really true and without considering the schedule.
For this reason, it is generally best to get your game to a playable and enjoyable state as soon as you possibly can, and then to rapidly iterate and improve upon it for the remainder of the project as often as you can find the time to. Enhancing the actual fun factor of your game should always be your guiding compass. Every choice you make about how to allocate your precious time and resources should be made in light of that perspective.
What you don’t want to happen is for you to spend months or years building up a bunch of assets to fill out your theme and world but then to only find out at the very end of the game development cycle that your assumptions about how your ideas would fit together were actually wrong. A theme is not a game.
Making your game fun as soon as possible and then rapidly iterating on it prevents this kind of devastating (but unfortunately quite common) scenario from happening. In fact, ideally, you want your game to not only be fun right from the start of the project, but also to be potentially releasable at any moment. You should aim to have all the basic functionality (e.g. menus, basic game mechanics, victory and loss conditions, etc) working as soon as possible.
Such a prototype is often referred to as a “minimum viable product”, but I often prefer to refer to it as a “fast-to-fun prototype” (a term I made up) as a reminder to focus on the fun factor above all else.
This game dev tip is an excerpt taken from a small book I wrote. You can find more information about the book here on my website.