overhauling wp_list_pages

Hi all.

I need to make a menu like the one at https://ideaskids.com using wordpress. So I need to completely overhaul the display of wp_list_pages. I cannot find where that function is defined in the wordpress php files, which is kind of weird.

I know that I can do this using child_of, and I might do this in the meantime to make them something that will work right away, but I want this to be easy for them to keep up to date, so I would like to edit the php files (since I don’t think I can do this with template tags, although that would be awfully nice … ) that determine the output of wp_list_pages. Logically, that function has got to appear somewhere so why can’t I find it?

I was looking at Blix, and I think if I found the right functions I could get it working. Basically, I need to set what should go around one top-level page, and what should go around a set of 2nd-level (first child) pages. I’ll need to build the link to the top level page.

Are there any thoughts on a good way to go about doing this?