I need more stimulation for the younger male cat I have. He can go outside all day and usually does but when he is in at night, he needs something to keep him occupied. I would prefer something he could do without me. Before I waste a lot of money on toys, does anyone have recommendations. I have a tree, a scratching post, I hide toys around and put a cardboard box and empty paper bag in the room. He seems to use all but I even need more. He will get revved up and bully my other cat who doesn't want to play.