HostConfig for adaptive cards in bot framework

I'm using the adaptive cards with the bot framework node.js SDK. Sending those adaptive cards to my users already succeeded. Now I want to go further:

On the site they tell you can customize the look and feel of the card further. Now I wonder how this works? How can I adjust this hostconfig file to change colors, padding, background etc. And how can I use CSS and HTML to build cards, like they say on the site?

Thanks in advance

via Stijn Brysbaert