How to Design a New Manager theme?

Hi, maybe i have asked the stupidest question?... but i don’t care!, have got an idea of the modx manager interface theme!, i am doing this just for fun, and am not making a money with modx or i am not in a hurry!, so help me to find out the right path to accomplish this.
i will make it available for the public use if i get it done.

Any suggestions on what are the steps!? -just mention it if you know.

Thanks

Copy the MODx default theme found in manager/media/style ... it’s all css and images for the most part.

Thanks rthrash