Did I mention that I’m an idealistic idiot?

Well, I am.

I have decided to make things even more complicated and am attempting to add worldbuilding into the visual representation of my game.
For reasons that will not be explained, the primary source of light (i.e. the sun) remains at the equivalent of noon during day-time.

So light will always come from straight above and reach the top surfaces primarily, the floor surfaces semi-primarily, and all other surfaces secondarily.
But light from a source as far away as the sun is will never reach us in perfectly parallel rays, so there will be some stray angles as well.

Let’s not complicate things too much more, though.
In order to get a feel for what this means, I’ve made a mock-up building that features no roof (well, actually it’s a set of walls, but nevermind that now).

Top surface is naturally the brightest, uniformly so, because the light comes straight down onto it.
Front surface is slightly darker as it receives less direct light.
There’s no shade in this picture as there is nothing casting a strong shadow.

However, shouldn’t I technically color the inner top surfaces of the windows and the doorway in the darkest shade? If light comes from straight above, it will cast a shadow onto what’s straight below it, right?

Well, in a way it does. But as I said, light will never reach us in a perfectly parallel beam of light, so chances are that there are enough angled sunrays that we can get away with not putting the color for more strongly shadowed surfaces there, but a lesser illuminated one than the very top surface.

If you pay enough attention, you can see that I’ve decided to give those edges a one pixel high line of the brightest shade in this palette.
Why? Chances are that enough light hits the edges to make it comparable to the top surface in intensity.
Also, there’s that direct reflection to the viewer thing still floating around in my head.
At any rate, it does give some depth to the image.

But see for yourself, here’s a version without said highlight.

If it were a matter of direct reflection to the viewer, wouldn’t that mean the top surface edges the closest to the viewer reflect light even more strongly than the top surface itself?
It’d look something like this:

Somehow, it doesn’t look right.
Maybe that’s my (flawed) understanding on how lighting and shading is supposed to work, ro maybe it’s my mind intuitively taking offense at something that looks wrong.

Who knows?
I sure don’t, so I’ll stick to the first version for the time being.