Expertly balancing one rock on top of another at the European Stone Stacking Championships, competitors combine skill and artistic creativity to come up with gravity-defying constructions.
Now in its third year, the event takes place in the Scottish coastal town of Dunbar, east of the capital Edinburgh.
Saturday's competition down on the Eye Cave Beach was all about quantity: the most stones balanced vertically in 30 minutes.
Sunday's battle put the emphasis on artistic merit: creating anything from stones or found objects within three hours.
The winner receives a trip to the Llano Earth Art Festival in Texas where the 2020 World Rock Stacking Championships will be held.
"Stone stacking is one of the most ancient art forms. It may go back to the beginning of mankind," organizer James Craig Page told AFP.
"However, it was brought to the attention of the public over the last 15 years by Bill Dan from California and more recently Michael Grab," two of the best-known artists.
"Events like Llano Earth Art Festival and its World Rock Stacking Championship, and the European Stone Stacking Championships, are helping to promote this ever-growing art form.
"The skills required to become an expert balancer artist are patience, focus, a love of nature and an unwillingness to be unhappy any more."
The abstract shapes produced by rocks eroded by the tides over the centuries means sculptures can be produced with impressive, seemingly gravity-defying angles.
Stone stacking also requires concentration and forethought to pull off the most dazzling creations.
France's "SP Ranza" was declared the overall winner, as well as winning the quantity category.
The winner in the artistic category was Marianne Winter, from the Netherlands, who came second overall.