It's generally hard to do much with CSS without understanding the HTML you're trying to style. Here's an template shared by many card views:
For example, here's what the relevant HTML might look like for the "open" view of a card named "Menu".
<div class="card-slot open-view card-frame ALL TYPE-basic SELF-menu">
<h1 class="card-header">...</h1>
<div class="card-body card-content ALL TYPE-basic SELF-menu">...</div>
</div>
Several key points warrant special attention:
Wagn strongly features nesting (eg, cards including cards). HTML/CSS, too, does lots of nesting. So be mindful of their interaction. For example, consider this CSS:
.open-view .card-content { font-weight: bold } #BOO!
On the face of it, this just looks like it's meant to make the content of cards in open view display as bold, and so it will. But it won't stop there; it will also apply to the content of any card included by a card in open view. This over-application pattern is very common in Wagn. Consider the following alternative:
.open-view > .card-content { font-weight: bold } #OK!
That extra ">" is important. It means this CSS rule should apply only to the .card-content that's a direct child of the open-view. Similarly, consider the following:
.SELF-menu { color: red } #BOO!
This is a common mistake. Usually it is intended to style only the content of the card named "Menu", but instead CSS rules of this kind can impact the header, help text, menu items, error messages, etc. If the intent is to style the content, then content should always be specified:
.SELF-menu.card-content { color: red } #OK!
Note that there is no space between ".SELF-menu" and ".card-content". This notation means: all tags with both the class "SELF-menu" and "card-content".
We might summarize the ideas as "no CSS rules on naked sets". Whenever you make a rule on a set without either a ">" or an additional class, you're at risk of over-application.