unity – How is 2D fog made in Graveyard Keeper?

I really like the fog effect of Graveyard Keeper, but I can not figure out how to do it. It's 2D, done in Unity, all the characters seem to be underneath & # 39; of fog, but the tops of tall trees and buildings stand out. Does it look like this –

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The developer has given some information about how it is done on this site:

http://www.gamasutra.com/blogs/SvyatoslavCherkasov/20181023/329151/Graveyard_Keeper_How_the_graphics_effects_are_made.php

Here it says: "As you can see, the upper part of the houses and the trees are seen from the fog, in fact, this effect is very easy to do." The fog consists of a large number of horizontal clouds scattered throughout the image. As a result, the top of all the sprites is covered with a smaller amount of fog sprites: "

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Following this information, in addition to looking at one of the developer's tweets that shows this image.

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(https://twitter.com/LazyBearGames/status/951811970310856704)

I tried to recreate it. When the character moves up or down on the screen, it flashes when it crosses each fog sprite –

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What have I missed?

All sprites are in the default classification layer and have a sort order of 0. The project, in Graphics Settings – Camera Settings, has the custom axis and the classification axis (0,1,0). The tree and character are in the same z position, and the fog extends over several z positions:

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