Belle is a VERY playful cat with us, and she is the only pet in our home - and is strictly an indoor cat. However, our neighbor's outdoor cat, Sugar, comes to visit Belle sometimes. He comes up onto our deck and sits in front of the sliding glass door (and Belle is on the inside of the door looking out), and he is clearly very mean to her. He puts his ears down, puts his tail down, and hisses and lunges at Belle (even though there is a door in between them - so neither cat gets hurt).
However, I'm really confused whether Belle is being mean back or if she's just trying to play with Sugar. She can't take her eyes off of him, and her tail swishes from side to side very fast (today it got poofy too), but her ears are up, and she doesn't hiss or growl at him. However, she sometimes 'lunges' at him or looks like she's trying to pounce on him...or sometimes she will hunch her shoulders the slightest bit while she's watching him hiss and spit at her. Is Belle being mean to Sugar or playing??