C2515 Grooves

"Yi, what is this!"

Suddenly, someone looked at the top of the pyramid in surprise. There was a pair of footprints there, as if it was some kind of mechanism, but it also seemed like someone had purposely left a footprint here. It was just that the footprint was a bit deep, almost five centimeters!

The other two also came over, and they looked curiously at the footprint. Then