I have a family of sites that are all similar, with some differences. Specifically, it's a collection of racing game sites, all with the same basic theme, but with site-specific CSS for certain pages that are related to each game.

As such, I will have different themes for each site - let's say they are mytheme1, mytheme2, and so on. For the css that is common to all themes, I want to put that in a file that is easily copied from one to another whenever I make changes. For the site-specific css, that can be in css files that are named specific to each theme.

This is what I tried... I copied all of the "pixture_reloaded" files into the folder for mytheme1 (the one I'm trying first). Everywhere I found "pixture_reloaded", I renamed it to mytheme1. That means that, among others, I have a file named /css/mytheme1.css. I also added a file named common.css (and added it to the .info file) and moved all the css from mytheme1.css into common.css. At this point, I was hoping to be able to modify the now empty mytheme1.css file and add css specific to site1.

Unfortunately, I had already enabled the theme once before moving the css out of mytheme1.css into common.css. I now realize that the mytheme1.css file is used to create files in /sites/default/files/adaptivetheme/mytheme1_files, so now all of the changes I make to common.css are still being overridden by the css that ORIGINALLY was in mytheme1.css (even though mytheme1.css is now empty).

I already read about the custom.css file, but that is actually the opposite of what I want. If I put site-specific css in the custom.css file, and leave all the common css in the mytheme1.css file, that means whenever I change something that is common to all themes, I will have to copy and rename mytheme1.css to mytheme2.css, and to mytheme3.css, and so on for nine themes. Much better if the common css was in a file with the same name - just copy, copy, copy - no renaming (with more chances for errors). And based on what I've described above, I don't see how to make those changes appear in the files that are in the /sites/default/files/adaptivetheme/mytheme{x}_files folders.

Would you please tell me:

a) How can I accomplish what I've described above?
b) How do I get the theme to recognize changes to the main css file (mytheme1.css in this example)?

Thank you in advance.