Twinball is a two-player pinball game where players are challenged to hit balls through their opponent’s goal while also using pinball arms to both hit and prevent the balls from falling into their goal. Players must also dodge several obstacles as they attempt to hit the balls to the opponent’s side, such as modular obstacles and battery-powered Scotch Yoke mechanism.

The final design included over 40 parts, with three distinct sub-assemblies: the ghost mechanism, the launcher mechanism, and the pinball arms mechanism.