Bartik only works for desktop-sized viewports because it hard codes pixel values in its layout CSS and assumes a significant amount of horizontal space in its navigational element design.
Convert Bartik’s design to be a responsive web design, including changing those width values from pixels to percentages.
- Convert the sidebar/main content, triptych, and footer areas to use media queries to use different numbers of columns in the layouts depending on viewport size. See comment #10
- Decide how to handle tabs, secondary links, and primary link navigation. See comment #10, comment #13 and comment #17
D7 backport at http://drupal.org/project/bartik_respondz.