I understand completely. I was there myself. Kind of still am but once you find what you are looking for and see it repeatedly, it becomes much clearer. CSS customization is almost limitless. You just have to find it. Once it's done, it's done. I've had to "relearn" what I've done to help out some friends as my main board was created many moons ago.
Your are absolutely right about the rabbit hole that is Tile Builder. I found CSS the same once I started to get the hang of it.
This is a long but great read. I have picked up alot of ideas from it. There are quite a few phone specific boards in there. It's amazing what some have accomplished.
