With a whirring sound and a click, the garage door swings open on its track, coming to rest with a clanking noise at the top. The area is dark, but your headlights break through the darkness and illuminate an empty space — your car is still in the driveway. It was so nice of you to come home early! You jog up to the garage door opener and reach for it, stopping dead in your tracks when you realize it's not there.