The game Happy Glass challenges a small, abstract, faceless figure to change the facial expression of a stained glass window on its face. In order to play, the player clicks and drags a small glass fragment from a palette onto the target area. Each attempt requires precision, as the glass flows and adapts to the shape of the target.
The interface is minimal, with a large playing area and a palette of available glass pieces. The game does not have a Start button, instead, it begins automatically. The player has freedom to move the glass pieces as needed to achieve the desired shape, while the in-game timer keeps track of progress.
The goal is to alter the expression on the glass window to six different states. Sometimes, this requires solving a straightforward problem, while in other cases, a creative, almost artistic approach is necessary. The requirement to achieve different emotional expressions is the core of the gameplay, encouraging quick thinking and creative control.