Great use of such a limited space! Instead of saying "I don't have much of a yard" you made it work.
At first I was trying to figure out why you enclosed the whole top, but with such narrow areas it could be possible for a smart cat to jump their way out.
man, happy cats you have there!
Do you have cat door for them to go out whenever they want? I am impressed! I love it! No w I want to get a house just to do something like that LOL