Lizzie chases shadows. In the morning, when the sun is shining into the living room, she will lay on the floor, waiting for birds to come to the feeders and make shadows on the floor for her. And when a bird does make a shadow for her, she will bite at shadow while animatedly wagging her tail.
In the winter, on sunny days when the snow can be formed into snowballs, we will throw snowballs in the air so that shadows move across the yard. Lizzie happily chases after those shadows, occasionally barking at them. If our timing and aim is right, the snowball will land on her back as she chases its shadow across the yard.
After the snow melted this spring, there was no handy shadow making materials. Kat got the idea of using balls and purchased a bag of cheap plastic balls. The slow-motion video below is of Lizzie chasing the shadow of a ball and then catching the ball.
In the above video, Lizzie is wearing a bandage on her right front paw. She had a torn nail that was causing her some discomfort, so we bandaged it up. She is all healed up now.