decrease knight center importance

src/evaluate.rs

@@ -108,7 +108,7 @@ fn knight_value(game: &Game, side: Side) -> PosValue {
     let center = (ROW_4 | ROW_5) & (FILE_D | FILE_E);
     let center_knights = (game.get_piece(KNIGHT, side) & center).count_ones() as PosValue;
     
-    center_knights * 20 + k_attacks as PosValue + ((num_knights * 75 * num_opp_pawns) / 8) as PosValue
+    center_knights * 6 + k_attacks as PosValue + ((num_knights * 75 * num_opp_pawns) / 8) as PosValue
 }
 
 fn material_value(game: &Game, side: Side) -> PosValue {