Source: https://codepen.io/smhigley/pen/gwYPvR Author: Sarah Higley License: MIT License. Slightly modified to be imported into projects a little more easily.
How to use:
add link with href to the css file in the header of your html file of choice and also add the below script element to import the js file
<script src="fallingLeavesEffect.js"></script>(also make sure you adjust paths for your individual case)