Abstract: A game board structure for a construction toy set. A basic game board is formed of three generally rectangular panel assemblies of hollow construction. The panels have interengaging projections and recesses for mechanically locking the panels together to form a flat playing surface for various rolling ball games, such as pinball and speedball. Joining of the panels automatically connects the panels together electrically for scoring and control functions throughout the board. The assembled game board accommodates mounting of a score-indicating panel in different locations, for different playing modes, such as pinball, typically played by one person, and head-to-head games, such as speedball, played by two persons.