Look they work!
It isn't as hard as it may seem. I've glued together some different sizes of wood so there is an opening were the window fits very tightly. Now it stays up when you move it.
Only the sides are like this. The rest is one piece. Then you use your mitre box and a tool to glue the frames rectangular, I use Lego for this. The glass in the windows is from a Ikea photo-frame named Ram . I read this tip on the internet and it works very good. It's plexiglass so you can cut it easily.
I also put in the electricity. I had to mill (is that how it's called?) for this for the first time, very exciting to try this!
And now we have light!! So I can finish the rooms with wallpaper and flooring if I want. I used 4 outlets in every room so I can choose my lamps later on.