the header transforms
Not exactly…the ‘transform’ merely makes sure it’s centered regardless of it’s width.
The width is actually changing.
is it possible to have a fixed header, centered, at 100% width?
Of course, that’s the more popular choice. Just set it to 100%.
You should, ideally, center the content of the 100% wide div/header rather than the header itself but there are multiple techniques for doing that.
fixed sliding headers?
It’s not a popular option….most fixed headers are 100% wide as I said.
With the media queries you are only concerned about the width of the header (or max-width depending on which way you go about it) and any margin (if that’s the way you go).
A quick google search will find you lots of examples of how to use media queries.