Linux mint cinnamon how to customize theme

Linux mint have two style theme- system theme and user theme

eg: system setting->themes like picture below:

Void is user theme and the other is system theme,system theme can‘t be uninstalled.

So the the file all about the theme will at different path,

system theme file at : /usr/share/themes/

user theme file at : ~/.themes/

all theme can be customized by edit .css file.

Linux Mint theme customize