The windows are opened enough to get a paw through, that’s all.
My cat managed to tear through the screen on our backdoor and quite proudly jumped through it to frolic in the yard. We were not as delighted with this development as him, as you can imagine.
**PURRS FOR BRIDGET!!! YEAH! **
I love happy endings! 
In his pre-house arrest days, our older cat Domino had an extensive con game going all up and down the street. He had several people convinced that he was a homeless pregnant mother. He also found a place where they kept the door open and the screen door shut… he stealthily widened that hole enough to admit his impressive bulk and helped himself to their cat’s dish. This went on for weeks, they told me, before they figured out why their cat was hungry all the time.