I recently adopted a new kitten last week who’s about 8 weeks old. I’ve kept her in my bedroom as her safe room because it’s the smallest room in my apartment & I wanted to let my resident cat, a gray shorthair who’s about 2-3 years old, have more room to move around in. I feed them on opposite sides of the bedroom door as suggested by most guides & have been trying to introduce them as slowly as possibly. On the first day, my resident cat hissed quite a bit, it’s the first time I had ever heard her hiss which worried me, but read that this is normal behavior. I rubbed both cats with socks & put the opposite sock with the other cat on the 2nd day to see how they’d react & both cats had no negative reactions. She stopped hissing on the 3rd day of my kitten being here so I decided to move it forward a bit. I kept feeding them across the door for the past week & tried to get them to play with a toy on both sides attached to a string, which they did for a short period of time. It’s been a week without hissing so I decided to try something I saw on Jackson Galaxy’s website. I put a screen in the doorway & sealed it so neither cat could get through & put a blanket over it & lifted it to slowly visually reveal the kitten to my resident cat. My resident cat started to get hostile & hissed at the kitten who seemed scared. I dropped the blanket over the screen & closed to door to help the kitten feel safer. I’m worried that I’ve put both of them in an uncomfortable/irreparable situation. My resident cat appeared to feel more comfortable around the scent of my new kitten, but I am unsure now. Is this common? Does anyone have any advice on how I can help my resident cat feel more comfortable in this situation?