Side menu (menu proxy) customization

[Olanko]

I have an HTML 5 project based on Top Navigation Advanced template. There's a menu proxy (side menu) inserted into a snippet that is applied to some topics. The side menu serves for navigating between those topics (naturally:-)). I want this menu to show only parent topics (=Categories), with children topics hidden. To open any topic of one category the links inserted in those topics are used. One more condition: the Category the selected topic refers to should be highlighted. Like this:

Category 1
Category 2
Category 3

I set up the menu to show only 1 level, Context Sensitive option is off.
The problem is that the Category (parent) doesn't get highlighted if a child topic is selected.
To make a long story short: I want the menu to look like the side menu of one of the madcapsoftware site section http://www.madcapsoftware.com/videos/. But when I navigate between the pages, the Categories are not shown highlighted (bold).
Any advice would be appreciated.

[NorthEast]

The menu example on the MadCap site isn't the same as what you describe; the highlighted page on the right is the current page (not the parent), and the other links are sibling pages at the same level.

You can set up your menu like this in the menu proxy; you'd select the context sensitive option and include siblings.
You can also choose whether to display child topics or the parent topic.

However, there's no style to highlight the parent, or any option to display siblings at the parent level (with the context sensitive option).
Highlighting the parent would probably need some scripting, since CSS doesn't have a parent selector.