The Muut Designer is great for quick and easy styling. However, if you want to get your hands dirty with CSS code, then your best bet is a DOM inspector, such as Chrome Debugger or Firebug, or Safari element inspector. Right click any element in Muut and choose “Inspect element” and you’ll see something like this:
You’ll see that Muut prefixes all CSS class names with “m-”. The purpose of this prefix is to avoid conflicts with other parts of your site.
There isn't much you can't do with Muut and CSS, including reordering elements as you wish. Get creative — but remember to add your own styles after the default CSS in order to protect your customizations against changes in newer Muut versions!