On Linux it takes a handle to the RootWindow and starts drawing on it, but if You are using a compositor it creates a new window with parameters similar to RootWindow. On Windows it works similar to the second case
If You don't like the idea of my project, You can just ignore it. I spent my free time to create this and I'm happy, that someone likes it. I train my programming skill and learn new thing by doing projects like this. I would never learn programming if I didn't play with it.