Customise Simple.css
Let's say you want to use Simple.css on your next project, but vanilla Simple.css doesn't provide enough - you want to add some classes and maybe change a few things. You can do that too.
First, create a new stylesheet in your project called anything you like - I'm going with custom.css, then add it right below the Simple.css stylesheet in your head:
<link rel="stylesheet" href="https://cdn.simplecss.org/simple.min.css">
<link rel="stylesheet" href="/path/to/custom.css">
From here you can edit custom.css to add your own rules. The best part is that if you add a rule that's already referenced in Simple.css, you custom.css rule will take precedence.
For example, if you want to change the accent colour from blue to red, you can simply add the following:
:root {
--accent: red;
}