body {
            background-color: #f8f9fa;
            font-family: 'Arial', sans-serif;
            font-size: 1.2rem;
            line-height: 1.8;
        }
        .container {
            max-width: 1100px;
            width: 100%;
            margin: auto;
        }
        h1 {
            font-size: 2.5rem;
        }
        h2 {
            font-size: 2rem;
        }
        h3 {
            font-size: 1.8rem;
        }
        h4 {
            font-size: 1.5rem;
        }
        .tabs {
            display: flex;
            justify-content: center;
            gap: 10px;
            margin-bottom: 30px;
            flex-wrap: wrap;
        }
        .tab-link {
            padding: 14px 24px;
            cursor: pointer;
            background: #e0e0e0;
            border-radius: 20px;
            border: none;
            font-size: 1.2rem;
            transition: background 0.3s, color 0.3s;
        }
        .tab-link:hover {
            background: #007bff;
            color: white;
        }
        .tab-link.active {
            background: #007bff;
            color: white;
            font-weight: bold;
        }
        .tab-content {
            display: none;
            padding: 10px;
            border-radius: 8px;
            background: #ffffff;
        }
        .tab-content.active {
            display: block;
        }
        .dialogue, .vocabulary, .grammar, .exercises, .reading {
            margin-bottom: 30px;
        }
        .dialogue-card, .passage-card, .vocab-card, .grammar-card, .glossary-card, .exercise-card {
            transition: transform 0.2s, box-shadow 0.2s;
            cursor: pointer;
            font-size: 1.1rem;
            border: 1px solid rgba(0, 0, 0, 0.125);
        }
        .dialogue-card:hover, .passage-card:hover, .vocab-card:hover, .grammar-card:hover, .glossary-card:hover, .exercise-card:hover {
            transform: translateY(-5px);
            box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
        }
        .audio-btn {
            font-size: 1.1rem;
            padding: 10px 20px;
            margin-bottom: 15px;
        }
        .note {
            font-style: italic;
            color: #555;
            font-size: 1rem;
        }
        #audio-feedback {
            display: none;
            position: fixed;
            top: 20px;
            right: 20px;
            z-index: 1000;
            max-width: 90%;
        }
        .vocab-card p, .grammar-card p, .glossary-card p, .exercise-card p {
            margin-bottom: 0.5rem;
        }
        .vocab-card strong, .grammar-card strong, .glossary-card strong, .exercise-card strong {
            color: #007bff;
        }
        .collapse-btn {
            font-size: 1.1rem;
            padding: 8px 16px;
            margin-bottom: 15px;
        }
        .draggable, .draggable-word {
            cursor: move;
            user-select: none;
        }
        .draggable.dragging, .draggable-word.dragging {
            opacity: 0.5;
        }
        .droppable, .droppable-sentence {
            min-height: 40px;
            border: 2px dashed #007bff;
            padding: 10px;
            background: #f8f9fa;
        }
        .droppable:hover, .droppable-sentence:hover {
            background: #e0e0e0;
        }
        .form-control.d-inline-block {
            width: 100px;
            display: inline-block;
            margin: 0 5px;
        }
        .alert-success, .alert-warning, .alert-danger {
            padding: 10px;
            border-radius: 5px;
        }
        .list-group-item {
            margin-bottom: 5px;
        }
        .collapse {
            margin-top: 15px;
            padding: 10px;
            background: #f8f9fa;
            border: 1px solid #dee2e6;
            border-radius: 5px;
        }
        @media (max-width: 576px) {
            body {
                font-size: 1.1rem;
            }
            h1 {
                font-size: 2rem;
            }
            h2 {
                font-size: 1.8rem;
            }
            h3 {
                font-size: 1.6rem;
            }
            h4 {
                font-size: 1.4rem;
            }
            .dialogue-card, .passage-card, .vocab-card, .grammar-card, .glossary-card, .exercise-card {
                font-size: 1rem;
            }
            .tab-link {
                font-size: 1rem;
                padding: 10px 18px;
            }
            .audio-btn, .collapse-btn {
                font-size: 1rem;
                padding: 8px 16px;
            }
            .form-control.d-inline-block {
                width: 80px;
            }
        }