Game of skills with balls running along system of passages

摘要

The movement of the balls (3) is controlled by phase limits between liquid (2) and gas. The phase limits in the form of gas bubbles (4) are freely movable and can be restricted in their movement by extra transverse struts. The system of passages consists of a single tube (1). The tube contains a gas bubble and four identical balls which can be split into two pairs of balls separated by the gas bubble by tilting the tube skilfully.