MyBB Community Forums

Hello developers/designers. 

I would like to know in general how to make any theme responsive? Can it happen like that? Can we make a global css file that would actually make the mybb responsive irrespective of the theme being used? Or is it theme dependent? 
In any case, what kind of code would actually work? What exactly do we need to change or manipulate to make the theme responsive? Or do we have to add the functionality from scratch? 
I know I'm a novice and this question would look dumb to many of you, but I'd appreciate if you could please answer. 

Thank you

basically responsiveness is theme dependent & it is not an easy task to make a theme responsive.

in general, @media css queries are used to resize elements of the page.

some theme coders also make bootstrap based designs

If you are not planning to add Bootstrap, better give these links a try

https://www.toptal.com/designers/respons...ia-queries

http://www.w3schools.com/css/css_rwd_mediaqueries.asp

Thank you for replying guys. So I know a bit about media queries before, and thanks to dilip's links I can learn more.
So if I would have to make a css file of media queries for my forum, what I would need to know apart from the media query css, all the IDs and class names of the elements of the theme I'm using right? Or is there anything else too?
And secondly, if I eventually be able to make such a file that makes my forum responsible, if I ever decide to change the theme of the forum, all I have to do is replace the id and class names of the css file according to the new theme? Will that work?