From the box:

"Careful! Careful! You never know,
The one you add may make it blow!"

A spinner is used to determine how many marbles each player in turn must drop in a hat that sits on top of a balloon-man's head. Small strips with a texture resembling extremely rough sandpaper are attached under the hat; these sit gently on the surface of the balloon-head. At some point, the weight of the marbles becomes too much and the hat-strips pop the balloon. The winner is the person with the fewest marbles in their posession when the balloon bursts.

The game was designed by the well-known Marvin Glass & Associates design studio.