A kinetic sculpture of the Greek mythological figure Sisyphus, endlessly pushing his boulder.
The video explains how it works and might help you see how it goes together if the instructions are unclear in any way.
One note about the assembly process. Depending on the relative orientation of the two crank shafts when you connect the chain, the motion of the legs and the body/boulder may not be in sync. It’s quite easy to adjust this after the fact – just slide the 12 tooth double bevel gear (the black one) to disengage the leg crank shaft, orient the two crank shafts as they are depicted in the instructions, then reengage the gear.