Neal Agarwal created this lovely and addicting rock-stacking simulator.
It delivers some of the meditative appeal of creating little stone cairns without the controversy. From National Geographic:
It's tempting to create your own as you travel, but that's not always a good idea: misplaced rock stacks can lead hikers off trail; endanger fragile ecosystems[…] or, if stones are pried loose for cairn-making, promote erosion.
The desire to stack rocks is understandable from a practical, aesthetic, and spiritual perspective. It seems almost primal. "As a species, we evolved in rocky landscapes," says David B. Williams, who wrote the book Cairns: Messengers in Stone. "We have been building these things for thousands of years. They're a way to say: I am here. I have lived."