Should I increase visual contact or wait?

Hello! This is my first time introducing cats so if the answer to the question is obvious, sorry in advance!

I’m introducing my resident cat to my new foster, so far things are going well. They eat and play in front of a pet gate with a blanket covering all but about 2 and a half inches from the ground up, but they’ve definitely seen more of each other. Two days ago I realized that my resident was trying to play with the foster. When in the room with my resident, I will sometimes play with the foster underneath the door with a toy. I was doing this last night with my resident sitting next to me. He would patiently watch, and when the foster stuck her paws under the door for the toy my resident would pounce at her paws. It looks purely playful from the resident (no meowing/hissing or puffy fur) but the foster would hiss anytime he did that. I think maybe she doesn’t realize that he’s trying to play. Would it be okay to increase visual contact at this point? Or should I wait until there’s no hissing at all? My hopes is that if the cats see more of each other that they could read the other’s body language more and maybe the foster would see that my resident is trying to play. Again, sorry if this is an obvious question, I’m just looking for some reassurance from others who have successfully introduced two cats before.