implemented checkmate

src/logic/pieces/knight.py

@@ -4,7 +4,7 @@ class Knight(Piece):
     def letter(self):
         return "n"
 
-    def legal_moves(self, board: "Board") -> list["Move"]:
+    def legal_moves(self, board: "Board", / , looking_for_check = False) -> list["Move"]:
         ret = []
         for dx, dy in [
             (+2, +1), (+1, +2), # north east
@@ -15,5 +15,9 @@ class Knight(Piece):
             move = self._move_for_position(board, self.pos.x + dx, self.pos.y + dy)
             if move is not None:
                 ret.append(move)
+
+        if not looking_for_check and board.is_check_for(self.colour):
+            return self.keep_only_blocking(ret, board)
+
         return ret