 But if you didn't have an optical fibre, you'd have to use a bunch of mirrors and lenses and stuff, which you can imagine would be quite hard, which is the game. So I should explain, it's like a table with a glass top to it. Then there are these six mirrors, three on each side, and then there are various obstacles in a way, like little film boxes, little cylinders, and then there's a brain at the end that you've got to get to. And so the laser's only going to blast in a straight line, so we've got to basically navigate the obstacle course using the mirrors, yeah? Go on then, James. Off you go. Oh, look, there's a green light. Come on.