It's best to extact this zip file before installing.

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#Variants

This theme has two variants, Light and Dark. In The OS, shadows
are stronger/darker when dark theme is enabled. The dark variant
is simply a stronger, slightly different version of the light
variant.

---
#Installation

Inside this ZIP file, there are two folders labeled "Light" and
"Dark." Inside each folder is an installation package. You just
need to open it to install it. It should show up in ShadowFX's
selector, no problem.

If you choose to change variants, just open the package of the
variant you wish to install. After you install the new variant,
reload the theme by reselecting the theme in ShadowFX.

The file names for both variants are the same, so that the new
variant will replace the one installed.

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#An Issue When Installing

I've encountered a very strange issue while testing. I couldn't
change the variant of this theme. Turns out, something went wrong
when installing a previous package and the installer can't replace
the zip file in my temp folder. This shouldn't happen to you, but
in case it does, here's how to fix it.

Go to your temp folder. Type "%temp%" without quotation marks into
a run box (press Win+R) or into an explorer path field (the
rectangle to the left of the search bar). Then find "AvalonCA.zip."
If it exists, delete it. This should fix the issue, try installing
the package again.

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#Removal

If you wish to remove this theme from your ShadowFX library,
you’ll need to go to ShadowFX’s themes folder since the program
does not have the ability to remove themes yet.

First find the Stardock folder in your Documents folder.
If you don’t see a folder named “Stardock” there, find it in your
PC’s Public Documents folder. Inside the Stardock folder should be
another folder named “ShadowFX.”

Default paths:
C:\Users\[Your User Account]\Documents\Stardock\ShadowFX\
or
C:\Users\Public\Public Documents\Stardock\ShadowFX\

After you’ve located the ShadowFX themes folder, simply delete
the folder named “AvalonCA," or if you've changed the name of
the installation package, delete the folder with that name.

ShadowFX’s built in themes are also in this folder, so please
be mindful of what you do here.