I have a game

"I have a game in which I put a small pebble on a sloping board, then roll a pencil towards it – each roll of the pencil, always from the same position, pushes the pebble further. I make a series of marks where the pebble stops. I’ve chosen the gradient, the pebble and the pencil, but the randomness throws up surprises which intuition, or measurement, never can. Is this nonsense?"

Harrison Birtwistle