I wouldn’t recommend linking an external javascript if you don’t know how reliable it is. If the remote script change, it could break your forum.
I suggest you create a new theme component in your admin panel instead. Name it something like “snowflake effect”.
Edit this new theme component.
-
In the Head tab, copy-paste the javascript code inside a
<script>HTML tag. -
In the CSS tab, paste the CSS code, without the
height: 100vh;part inbody {. -
In the Footer tab, paste 176 times
<div class="snow"></div>. -
Enjoy your snow.
Note that this effect was created by someone in their own HTML environment, isn’t “Discourse-compatible” out of the box and thus it may cause issues on your forum.