It's a bit embarrassing, but although
CopperCube is already in version 5, and now about 7 years old, it still doesn't support fog. (Well unless you add this by writing your own shaders). But fog is a pretty cool feature, especially for the lightweight targets like WebGL and Android. So I started adding this:
It looks very nice, especially when used with terrain. Works also with the reflecting realtime water, I didn't even have to change a line of code for that, interestingly.
This new feature - fog - will be included in the next free update of CopperCube.