Editing themes is easy, you can change look and feel using CSS or PHP files for any theme. You have to have some experience editing those files before.
Keep in mind if you wan tto edit theme copy it to other folder and rename. Then edit your renamed copy in order to not delete your changes on theme update.
You can download and view Base theme files if you want to see the code. Download Base Theme to view code (This file may be not the latest version, it is only for demonstration of code. If you want to download latest version please log in to member area.)
PS: We suggest using Netbeans (https://netbeans.org/) for PHP to edit script files. Classibase is developed using netbeans. You can navigate to function and method declaration by clicking CTRL + "left mouse key" in netbeans.