Connect Four, but quantum and bigger.
With each turn the player has two different options. Either he chooses one column for a classical piece, or he chooses one or two columns for quantum pieces. The new pieces drop down as far as possible. They get enumerated in both cases which can get important in order to appoint the winner later on.
Measurements result in a collapsed wave-function. Therefore, the corresponding quantum pieces lose their positional uncertainty. This means that one of the two pieces becomes a classical one and the other one disappears with a 50% probability each, making space for the pieces above.
Quantum pieces get measured as soon as a classical piece lies upon it which can turn into a cascade of measurements.
As soon as (at least) one player managed to place psi (in the basic version 4) pieces in a vertical, horizontal or diagonal row the game is over.
In case several players achieved this goal at the same time due to a measurement, the one who would have completed his row fist, won.
The game is suitable for up to six persons. Furthermore, the boards` size as well as the number of pieces needed to win, can be adjusted.