body {
            font-family: 'Inter', sans-serif;
            background-color: #f3f4f6; /* Tailwind gray-100 */
        }
        .grid-container {
            display: grid;
            grid-template-columns: repeat(9, minmax(0, 1fr));
            gap: 4px;
            width: 100%;
            max-width: 500px; /* 最大幅を設定 */
            margin: auto; /* 中央寄せ */
        }
        .seat-cell, .area-cell, .result-cell {
            width: 100%; /* 親要素いっぱいに広がる */
            aspect-ratio: 1 / 1; /* 正方形を維持 */
            display: flex;
            justify-content: center;
            align-items: center;
            border: 1px solid #d1d5db; /* Tailwind gray-300 */
            border-radius: 0.375rem; /* Tailwind rounded-md */
            font-size: 0.875rem; /* Tailwind text-sm */
            transition: background-color 0.2s;
        }
        .seat-cell input {
            width: 100%;
            height: 100%;
            text-align: center;
            border: none;
            background-color: transparent;
            font-size: 0.875rem; /* Tailwind text-sm */
            padding: 0;
            border-radius: 0.375rem; /* Tailwind rounded-md */
        }
        .seat-cell input:focus {
            outline: 2px solid #3b82f6; /* Tailwind blue-500 */
        }
        .area-cell.selected {
            background-color: #60a5fa; /* Tailwind blue-400 */
            color: white;
        }
        .area-cell:not(.selected) {
            background-color: #e5e7eb; /* Tailwind gray-200 */
        }
        .result-cell.occupied {
            background-color: #ffffff; /* Tailwind white */
        }
        .result-cell.special {
            background-color: #fde047; /* Tailwind yellow-300 */
            font-weight: bold;
        }
        .result-cell.empty { /* 以前の x-mark の代わりに空席を示す */
            background-color: #e5e7eb; /* Tailwind gray-200 */
        }
        .section-title {
            font-size: 1.25rem; /* Tailwind text-xl */
            font-weight: 600; /* Tailwind semibold */
            margin-bottom: 0.75rem; /* Tailwind mb-3 */
            color: #1f2937; /* Tailwind gray-800 */
        }
        .control-panel label {
            display: block;
            margin-bottom: 0.25rem; /* Tailwind mb-1 */
            font-weight: 500; /* Tailwind medium */
            color: #374151; /* Tailwind gray-700 */
        }
        .control-panel input[type="text"] {
            width: 100%;
            padding: 0.5rem; /* Tailwind p-2 */
            border: 1px solid #d1d5db; /* Tailwind gray-300 */
            border-radius: 0.375rem; /* Tailwind rounded-md */
            margin-bottom: 0.75rem; /* Tailwind mb-3 */
        }
        .btn {
            padding: 0.75rem 1.5rem; /* Tailwind px-6 py-3 */
            border-radius: 0.375rem; /* Tailwind rounded-md */
            font-weight: 600; /* Tailwind semibold */
            transition: background-color 0.2s;
            cursor: pointer;
            text-align: center;
        }
        .btn-primary {
            background-color: #3b82f6; /* Tailwind blue-500 */
            color: white;
        }
        .btn-primary:hover {
            background-color: #2563eb; /* Tailwind blue-600 */
        }
        .btn-secondary {
            background-color: #6b7280; /* Tailwind gray-500 */
            color: white;
        }
        .btn-secondary:hover {
            background-color: #4b5563; /* Tailwind gray-600 */
        }
        .message-box {
            padding: 0.75rem;
            border-radius: 0.375rem;
            margin-top: 1rem;
            text-align: center;
        }
        .message-box.error {
            background-color: #fee2e2; /* Tailwind red-100 */
            color: #b91c1c; /* Tailwind red-700 */
            border: 1px solid #fecaca; /* Tailwind red-200 */
        }
        .message-box.success {
            background-color: #dcfce7; /* Tailwind green-100 */
            color: #15803d; /* Tailwind green-700 */
            border: 1px solid #bbf7d0; /* Tailwind green-200 */
        }