I subscribe to a site about cat's health. I was reading that all cats need mental stimulation. Cats are one of the most intelligent of animals. I have always known this but with two cats that chase each other around the house constantly, I didn't think that they would need stimulation. After a couple of days of thinking about this, I went on line to look for web sites for cat toys. They had become bored with the cat nip toys, balls and their cat tree. They like the tree most of all but they have begun to use it as a bed, rather than an exercise toy. Now, after seeing how much fun they are having, I will have to schedule purchases or make toys for them. Penelope can't stop playing. Chester likes the cat nip that I laced the card board scratching round. As I said before, Penelope really does know what looks good on her. She is a natural star, what charisma!