Where the Phph Pebbles Go

"Where the Phph Pebbles Go" by Miriam Allen De Ford is a science fiction tale set on an alien planet, where the inhabitants are keen on a unique game called "phph," which involves launching pebbles at a far-off target. This game is a casual event for the players, Gral and Hodnuth, watched by their people and the simple Ground Dwellers, but it becomes much more when the Thinkers, the planet's brain power, start paying attention because they are concerned about signals they've gotten from far away. These signals suggest other life exists beyond their world, leading them to worry that the pebbles from the game may travel to other planets and reveal their existence, possibly affecting their society; turning the game phph into a planet-changing event when they scheme to confuse alien observers by creating artificial pebbles.