What are some signs that a cat has stopped enjoying a play session and is now feeling overstimulated? My cat seems to switch from "lol i am fierce kitty!! *nibbles*" to "ok I'm done that's ENOUGH. *snap*" on a dime. I feel like there must be some change in body language I'm not picking up on? (For the record, I live alone, so I don't have to worry about her snapping at other people or anything. I just don't want her to be uncomfortable.)
I’d watch for pupil dilation and a change in tail motion, but honestly, it tends to happen pretty quickly and can be hard to watch for. For lots of cats it’s more of a hair trigger than a slow build. Another thing you can do is figure out what types of touch make them overstimulated and then make sure to never do that for very long - base it off observational data from previous situations, rather than body language in the moment.