pure css parallax in one file
npm install parallax.css
yarn add parallax.css
<link rel="stylesheet" href="node_modules/parallax.css/parallax.css">
or
@import 'node_modules/parallax.css/parallax.css';
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/parallax.css">
or
@import url(https://cdn.jsdelivr.net/npm/parallax.css);
You can find the Parallax.css documentation on github-pages.