Stylesheet

Without RFUI's stylesheet the RFUI components will be unstyled. For example, if you don't have the stylesheet, Checkbox will look like this:

instead of this:

To ensure the components look as they are intended to look, you will need the stylesheet.

<link
  rel="stylesheet"
  href="https://rfui.deno.dev/rfui.css"
/>

Be sure to think about which CSS rules take precedence over other CSS rules. Ie. if you have custom styles of your own, do you want them to take precedence over RFUI's styles? If so you'll probably want to place the <link> tag underneath <link rel="stylesheet" href="https://rfui.deno.dev/rfui.css" /> and give your rules the appropriate specificity.