As clever as robotic cars may be, they have one obvious disadvantage over flying drones: their journey stops the moment they run into a wall. Disney Research and ETH Zurich have a clever workaround, however. Their prototype VertiGo robot uses two tilting propellers to drive up walls, adjusting its thrust to stick to the surface even if it has to travel over uneven surfaces like bricks. The result, as you'll see below, is uncanny -- all it takes is a quick push from the propellers to have this machine defying gravity.