Responsive MainMenu for D7 I am struggling with Drupal menu. Currently my menu is not responsive. I know how to change it to become responsive using CSS. But I am wondering If there is any module that can do this easily. 

Please give any menu module if available to be responsive and adaptive to different screen sizes or suggest me if there are any simple tweaks.
This is hard to answer, because it depends very much on how your menu is designed and which navigation method you're going to use.

There's a sandbox project for the omega theme though.

Maybe this will help as well: Complex Navigation Patterns for Responsive Design