So, Prince and Nikita will always be indoor only (they've not tried to go outside either, though Prince has at least twice in the six months I've had him tried to casually walk past me when I enter the door, which led me to gently nudge him back inside). I've changed my bedroom around and took off the sheet I had over the window (My cats love sitting in front of it now) and I thought to open the window, letting air in and such. There's a screen in place and watching them yesterday and today, they've only sat or laid in front of it, so they haven't tried to claw through it or anything (So I hope having the window is okay); but today my downstairs neighbor has been outside the apartment with her kid, and there's car noises too, so I'm watching my cats walk around the living room and every now and then, like a meerkat, stop and look towards the bedroom door with ears raised. Prince tried to go up to the refrigerator at one point, so I'm not sure if he's scared of the outside noises or not. They don't act anxious, just curious and confused when they hear people. Like yesterday, my neighbor walked out of her apartment (the window overlooks the stairwell, and I'm on the second floor), and Prince stood up on the cat tree in front of the window and leaned forward like trying to watch and see what was going on. It's interesting because he is accustomed to other people, though no one's been over at my apartment for some time now, so they may or may not be nervous around other humans. I know when Nicole was over, they had no problem with her.