I'd like to make a legacy D6 site's theme more responsive. I love to be able to use the omni-present twitter bootstrap theme or something that comes close to it in responsiveness. I know that there is a quite a few for drupal 7+ but could not fine any for D6 on Drupal site.
So I'm wondering if there is any mature D6 Bootstrap theme? And if not, how hard is it to convert a D7 theme to D6?