Great idea for a puzzle game, mechanics feel very good. I got stuck on the third level for a while until i realised i can arrange windows vertically then horizontally, i couldn't figure that out because when you drag the window to the edge of the inner screen window's edges go out of the screen's edges. I also felt like difficulty increased fast though you should mind that i don't play much puzzle games. Besides these issues i had i had a good time, great job!