* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            display: flex;
            justify-content: center;
            align-items: center;
            min-height: 100vh;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
        }

        .container {
            text-align: center;
            padding: 20px;
        }

        h1 {
            color: white;
            margin-bottom: 20px;
            text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
        }

        .board-wrapper {
            display: inline-block;
            padding: 30px;
            background: #2c3e50;
            border-radius: 10px;
            box-shadow: 0 10px 40px rgba(0,0,0,0.3);
        }

        .chess-board {
            display: grid;
            grid-template-columns: repeat(8, 70px);
            grid-template-rows: repeat(8, 70px);
            border: 3px solid #1a252f;
            box-shadow: 0 0 20px rgba(0,0,0,0.5);
        }

        .square {
            width: 70px;
            height: 70px;
            display: flex;
            justify-content: center;
            align-items: center;
            font-size: 45px;
            cursor: pointer;
            transition: all 0.2s ease;
            user-select: none;
        }

        .square.light {
            background-color: #f0d9b5;
        }

        .square.dark {
            background-color: #b58863;
        }

        .square:hover {
            filter: brightness(0.9);
        }

        .square.selected {
            background-color: #7fa650 !important;
            box-shadow: inset 0 0 15px rgba(0,0,0,0.3);
        }

        .square.valid-move {
            position: relative;
        }

        .square.valid-move::after {
            content: '';
            position: absolute;
            width: 22px;
            height: 22px;
            background-color: rgba(0,128,0,0.4);
            border-radius: 50%;
        }

        .square.valid-move.has-piece::after {
            width: 60px;
            height: 60px;
            background-color: transparent;
            border: 3px solid rgba(255,0,0,0.5);
            border-radius: 50%;
        }

        .square.in-check {
            background-color: #ff6b6b !important;
        }

        .controls {
            margin-top: 20px;
        }

        button {
            padding: 12px 30px;
            font-size: 16px;
            background-color: #3498db;
            color: white;
            border: none;
            border-radius: 5px;
            cursor: pointer;
            margin: 0 10px;
            transition: background-color 0.3s ease;
            box-shadow: 0 4px 6px rgba(0,0,0,0.2);
        }

        button:hover {
            background-color: #2980b9;
        }

        button:active {
            transform: translateY(2px);
            box-shadow: 0 2px 4px rgba(0,0,0,0.2);
        }

        .game-status {
            color: white;
            font-size: 18px;
            margin-top: 15px;
            padding: 10px;
            background-color: rgba(0,0,0,0.3);
            border-radius: 5px;
            display: inline-block;
        }

        .message {
            color: #ffeb3b;
            font-weight: bold;
            margin-top: 10px;
            min-height: 25px;
        }