gobang/lib/models/chess.dart

import 'package:flutter/material.dart';
import 'package:gobang/models/chess_shape.dart';
import 'package:gobang/models/circle_shape.dart';

/// 棋子抽象类（桥接：颜色与外观分离）
/// 颜色为享元内部状态；实际绘制以外层 Position.chessShape 为准。
abstract class Chess {
  Color get color;

  ChessShape get chessShape;
}

class BlackChess extends Chess {
  @override
  Color get color => Colors.black;

  @override
  ChessShape get chessShape => CircleShape();
}

class WhiteChess extends Chess {
  @override
  Color get color => Colors.white;

  @override
  ChessShape get chessShape => CircleShape();
}