>Because if you do autozoom, it would make sense if it were to the smallest, possible zoom. Doing autozoom to an arbitrary level feels weird.

I think this way the player would have way more control about the zoom, and still it would continously autozoom in and out.

>Yes, true. Then maybe store max possible zoom range instead of deepest Y.

Aye, I was onto trying that out. It should only autozoom, when darkness has decreased/increased by a significant value. Let's say if current view range changes more then 100, from the last minimum view range, it should zoom out.
So I'm figuring out how to detect, wether it has changed by 100 or not.
But it seems like I can't use the same principle like

deepest_y = Max(GetY(), deepest_y);

because deepest_y is always equal to GetY().

Then again, I'm not sure if it's ok, if the zoom behaves like this:
You are somewhere dark, it zooms in for you. You could still zoom in manually. You go somewhere bright, but view range only changes by 99. It still doesn't zoom for you, and you can zoom how you want. Let's say you zoom in on this point, because you want to. You go one step further into the bright and all of a sudden it zooms out, because now it changed by 100.
At these thresholds the zoom could just jump out, even if the player doesn't want it to.

I have drawn a picture to illustrate how I think it should work. Also everyone loves pictures.
Oh crud I'm sorry, it cut out the name of the Y axis. Y axis is Viewrange!