extern Bitboard InFrontBB[2][8];
extern Bitboard StepAttacksBB[16][64];
extern Bitboard BetweenBB[64][64];
+extern Bitboard DistanceRingsBB[64][8];
extern Bitboard ForwardBB[2][64];
extern Bitboard PassedPawnMask[2][64];
extern Bitboard AttackSpanMask[2][64];