Themes: Override Stylesheet Only If It Exists?

I’d like to use themes only for CSS and image differences, so my themes will probably only have /css and /images folders. Ideally, I would only put in the files that are different for the theme from the basic configuration. I’m not sure if there is a default way to do that in Yii. If I use the Yii::app()->theme->baseUrl in my references, that will tie me to a specific theme. Is there a built-in call that will load the specific css file for that theme if it exists, but default to the basic one if it does not?

Load the main style sheets as ususal.

Then load the theme style sheets.

What is defined in the theme css will override what came before them.

That’s how CSS works. :)

Thank you. I’m aware of that, but I was trying to optimize loading. What I’ve done is set up a themes folder in which any files that exist, whether images or css files, are used instead of the default theme. My includes call a method that looks to see if the file exists in the theme, but defaults if it doesn’t. I ran it in a loop thousands of times to see if it impacts performance, and it is insignificant. I also have a theme.css where I can do the usual css overrides of individual styles.