SCSS Installation:
Atfirst install "node.js" in you windows system.
create a folder name "practice" in your desktop. then create a folder name "css" into it. Then create a file "custon.scss" into it. Then follow this steps: open cmd, then follow this process:
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C:\Users\users name>
C:\Users\users name>npm install -g sass
C:\Users\users name>cd Desktop
C:\Users\users name\Desktop>cd practice
C:\Users\users name\Desktop\practice>sass css/custom.scss css/custom.css
C:\Users\users name\Desktop\practice>sass --watch css/custom.scss css/custom.css