Stretching Youtube video over multiple passges or embedding in stylesheet?

Hi,

I've started playing around in Twine 2 (working in Harlowe 1.0.1) and recently discovered how to embed video within passage (using html) and how to fool around with background colour, etc. settings in the stylesheet (using CSS).

My coding knowledge is rather lacking and was wondering if it is possible to either stretch a youtube video (i'm using it as background music) over multiple passages or embed a video within the stylesheet. I've tried finding answers but so far my search has come up empty.

Any help or guidance will be much appreciated!