A determined state is defined as a state were one player has a winning semi/full connection.
In a winning state, returns key of smallest semi connection, if one exists. If no semi connection, plays move that overlaps the maximum number of full connections.
In a losing state, returns move overlapping the most SCs (instead of VCs) since any winning SC still remaining on our opponent's next turn will allow them to win. Thus, we want to eliminate those winning SCs that are shortest/easiest to find. It is also possible that our opponent has winning VCs and yet no winning SCs. In this case, we just perform the overlap with the VCs.