Why?

My cat Olive gets a little lonely around the house sometimes, so I wanted to make something that could keep him entertained while I'm gone. Thanks to this handy object-detection design, Olive can turn his toy on and off whenever he wants (if he ever wants to...).

When something or someone passes over the detector, the toy turns on and will remain until the detector detects a second. The elevated platform encourages Olive to pass by the photoresistor when he is walking near the toy. If you turn this project into a dog toy, it might find a bit more use; Olive didn't seem very interested.