feat: exclude pawncontrolled squares from mobility

2 files changed, 13 insertions, 2 deletions

diff --git a/src/board/engine.rs b/src/board/engine.rs
index 10fb604..6491289 100644
--- a/src/board/engine.rs
+++ b/src/board/engine.rs
@@ -263,7 +263,7 @@ impl Board {
         let king_tropism_penalty = self.king_tropism(color) - self.king_tropism(opponent_color);
 
         material_advantage
-            + 0.1 * mobility_advantage
+            + 0.15 * mobility_advantage
             - 0.3 * pawn_structure_penalty
             + king_tropism_penalty * (opponent_material / 40.0) * 0.07
     }
diff --git a/src/board/mod.rs b/src/board/mod.rs
index 8d12a12..fd0ff25 100644
--- a/src/board/mod.rs
+++ b/src/board/mod.rs
@@ -434,9 +434,20 @@ impl Board {
     pub fn mobility(&self, color: Color) -> f32 {
         let mut mobility = 0.;
         let opponent_occupancy = self.color_occupancy(color.flip());
-        let empty = self.empty();
         let player_pieces = self.pieces_by_color(color);
 
+        let opponent_pawns = match color {
+            Color::Black => self.pieces[PieceType::Pawn as usize],
+            Color::White => self.pieces[PieceType::PawnBlack as usize],
+        };
+
+        let pawn_attacked_squares = serialize_bitboard(opponent_pawns).iter().fold(0u64, |acc, square| {
+            acc | self.attacks.pawn[color.flip() as usize][*square as usize]
+        });
+
+        // Exclude squares controlled by enemy pawns from mobility
+        let empty = self.empty() & !pawn_attacked_squares;
+
         for (piece_type, piece) in player_pieces.iter().enumerate() {
             match PieceType::from(piece_type) {
                 PieceType::Pawn => {