In the game of Spades, if two players from opposites partnerships bid Nil, then the round plays very differently from a regular round. This is because that each of the non-Nil players is trying to set their opponent Nil without setting their partner.
For the sake of the rest of the discussion, let's call the players A, B, C, and D, where B and C are the ones who made the nil bids, so A and D are leading rounds after the first (unless one of B or C takes a trick). Here are some specific considerations:
- Player A (the cover-partner that plays before both Nilers), has a disadvantage, she don't know if she should play high card to cover her partner or she can play a low card to try setting her opponent's nil.
- Player D (The cover-partner that plays after both Nilers), has an advantage since she can see if she needs to cover or not.
I build an AI player of Spades, and I want to add this special case of Nil Vs. Nil round. My question is, what are the main strategy considerations, or what adjustments in game play should I add? For refining reasons, assume its the first round of the game.
 Nil Vs Nil rounds are not too rare in normal games. In the Suicide variant, every round is Nil Vs Nil.
 Occasionally, Nil Vs. Nil rounds happens at a "game winner round", that is to say, one partnership will win the game if she makes the Nil. In this kind of situations, other considerations come in to play. In order to refine the question, assume non of the partnerships is close to the game winning score.