:root {
            --sage-light: #e8f5e9;
            --sage-medium: #c8e6c9;
            --sage-dark: #a5d6a7;
            --beige: #f5f5dc;
            --off-white: #fafafa;
            --dark-green: #2e7d32;
            --dark-green-light: #388e3c;
            --text-dark: #1b5e20;
            --text-body: #333;
            --error: #c62828;
            --error-light: #ffebee;
            --success: #2e7d32;
            --success-light: #e8f5e9;
            --warning: #f9a825;
        }
        
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        
        body {
            font-family: Georgia, 'Times New Roman', serif;
            background-color: var(--off-white);
            color: var(--text-body);
            line-height: 1.6;
            font-size: 16px;
        }
        
        /* Header */
        header {
            background: linear-gradient(135deg, var(--sage-light) 0%, var(--beige) 100%);
            border-bottom: 3px solid var(--dark-green);
            padding: 1rem;
            position: sticky;
            top: 0;
            z-index: 100;
            box-shadow: 0 2px 8px rgba(0,0,0,0.1);
        }
        
        .header-content {
            max-width: 900px;
            margin: 0 auto;
            display: flex;
            justify-content: space-between;
            align-items: center;
            flex-wrap: wrap;
            gap: 1rem;
        }
        
        .logo {
            font-size: 1.5rem;
            font-weight: bold;
            color: var(--dark-green);
            text-decoration: none;
            display: flex;
            align-items: center;
            gap: 0.5rem;
        }
        
        .logo::before {
            content: "📚";
        }
        
        .exercise-indicator {
            background: var(--dark-green);
            color: white;
            padding: 0.5rem 1rem;
            border-radius: 20px;
            font-size: 0.9rem;
            font-weight: bold;
        }
        
        /* Navigation */
        .nav-bar {
            background: var(--sage-light);
            padding: 1rem;
            border-bottom: 1px solid var(--sage-medium);
        }
        
        .nav-content {
            max-width: 900px;
            margin: 0 auto;
            display: flex;
            justify-content: space-between;
            align-items: center;
        }
        
        .nav-btn {
            padding: 0.75rem 1.5rem;
            border: 2px solid var(--dark-green);
            background: white;
            color: var(--dark-green);
            text-decoration: none;
            border-radius: 8px;
            font-weight: bold;
            transition: all 0.3s ease;
            display: inline-flex;
            align-items: center;
            gap: 0.5rem;
        }
        
        .nav-btn:hover:not(.disabled) {
            background: var(--dark-green);
            color: white;
            transform: translateY(-2px);
        }
        
        .nav-btn.disabled {
            opacity: 0.4;
            cursor: not-allowed;
            border-color: #999;
            color: #999;
        }
        
        /* Main Content */
        main {
            max-width: 900px;
            margin: 0 auto;
            padding: 2rem 1rem;
        }
        
        h1 {
            color: var(--dark-green);
            font-size: 2rem;
            margin-bottom: 0.5rem;
            border-bottom: 3px solid var(--sage-medium);
            padding-bottom: 0.5rem;
        }
        
        .subtitle {
            color: var(--text-dark);
            font-style: italic;
            margin-bottom: 2rem;
            font-size: 1.1rem;
        }
        
        /* Progress Bar */
        .progress-container {
            background: var(--beige);
            padding: 1.5rem;
            border-radius: 12px;
            margin-bottom: 2rem;
            border: 2px solid var(--sage-medium);
        }
        
        .progress-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 0.5rem;
            flex-wrap: wrap;
            gap: 0.5rem;
        }
        
        .progress-bar {
            width: 100%;
            height: 20px;
            background: white;
            border-radius: 10px;
            overflow: hidden;
            border: 2px solid var(--sage-medium);
        }
        
        .progress-fill {
            height: 100%;
            background: linear-gradient(90deg, var(--dark-green) 0%, var(--dark-green-light) 100%);
            width: 0%;
            transition: width 0.5s ease;
        }
        
        .complete-checkbox {
            display: flex;
            align-items: center;
            gap: 0.5rem;
            cursor: pointer;
            font-weight: bold;
            color: var(--dark-green);
        }
        
        .complete-checkbox input {
            width: 20px;
            height: 20px;
            cursor: pointer;
        }
        
        /* Collapsible Sections */
        .section {
            background: white;
            border-radius: 12px;
            margin-bottom: 1.5rem;
            border: 2px solid var(--sage-medium);
            overflow: hidden;
            box-shadow: 0 2px 8px rgba(0,0,0,0.05);
        }
        
        .section-header {
            background: linear-gradient(135deg, var(--sage-light) 0%, var(--beige) 100%);
            padding: 1.25rem;
            cursor: pointer;
            display: flex;
            justify-content: space-between;
            align-items: center;
            border: none;
            width: 100%;
            font-size: 1.2rem;
            font-weight: bold;
            color: var(--dark-green);
            font-family: inherit;
            transition: background 0.3s ease;
        }
        
        .section-header:hover {
            background: linear-gradient(135deg, var(--sage-medium) 0%, var(--sage-light) 100%);
        }
        
        .section-header::after {
            content: "▼";
            font-size: 0.8rem;
            transition: transform 0.3s ease;
        }
        
        .section-header.collapsed::after {
            transform: rotate(-90deg);
        }
        
        .section-content {
            padding: 1.5rem;
            display: block;
        }
        
        .section-content.collapsed {
            display: none;
        }
        
        /* Typography */
        h2 {
            color: var(--dark-green);
            margin: 1.5rem 0 0.75rem 0;
            font-size: 1.4rem;
        }
        
        h3 {
            color: var(--text-dark);
            margin: 1.25rem 0 0.5rem 0;
            font-size: 1.2rem;
        }
        
        p {
            margin-bottom: 1rem;
        }
        
        .german-example {
            background: var(--sage-light);
            padding: 1rem 1.5rem;
            border-radius: 8px;
            margin: 1rem 0;
            border-left: 4px solid var(--dark-green);
            font-family: 'Courier New', monospace;
            font-size: 1.1rem;
            position: relative;
            cursor: pointer;
            transition: all 0.3s ease;
        }
        
        .german-example:hover {
            background: var(--sage-medium);
            transform: translateX(5px);
        }
        
        .german-example .translation {
            color: var(--text-dark);
            font-style: italic;
            font-family: Georgia, serif;
            font-size: 0.95rem;
            margin-top: 0.5rem;
            padding-top: 0.5rem;
            border-top: 1px dashed var(--dark-green);
            display: block;
        }
        
        .highlight {
            background: var(--beige);
            padding: 0.2rem 0.4rem;
            border-radius: 4px;
            font-weight: bold;
        }
        
        /* Tooltips */
        .tooltip-term {
            border-bottom: 2px dotted var(--dark-green);
            cursor: help;
            position: relative;
            color: var(--dark-green);
            font-weight: bold;
        }
        
        .tooltip-content {
            display: none;
            position: absolute;
            bottom: 100%;
            left: 50%;
            transform: translateX(-50%);
            background: var(--dark-green);
            color: white;
            padding: 0.75rem 1rem;
            border-radius: 8px;
            font-size: 0.9rem;
            font-weight: normal;
            width: 250px;
            max-width: 90vw;
            z-index: 10;
            box-shadow: 0 4px 12px rgba(0,0,0,0.2);
        }
        
        .tooltip-term:hover .tooltip-content {
            display: block;
        }
        
        /* Checklist */
        .checklist {
            background: var(--beige);
            padding: 1.5rem;
            border-radius: 8px;
            margin: 1.5rem 0;
        }
        
        .checklist ol {
            margin-left: 1.5rem;
        }
        
        .checklist li {
            margin-bottom: 0.75rem;
            padding-left: 0.5rem;
        }
        
        /* Exercises */
        .exercises-section {
            background: white;
            border-radius: 12px;
            padding: 2rem;
            border: 3px solid var(--dark-green);
            margin-top: 2rem;
        }
        
        .exercises-header {
            color: var(--dark-green);
            font-size: 1.8rem;
            margin-bottom: 1.5rem;
            text-align: center;
            border-bottom: 2px solid var(--sage-medium);
            padding-bottom: 1rem;
        }
        
        .exercise {
            margin-bottom: 2.5rem;
            padding-bottom: 2rem;
            border-bottom: 2px solid var(--sage-light);
        }
        
        .exercise:last-child {
            border-bottom: none;
        }
        
        .exercise-title {
            font-weight: bold;
            color: var(--dark-green);
            margin-bottom: 1rem;
            font-size: 1.2rem;
        }
        
        .exercise-item {
            margin-bottom: 1.5rem;
            padding: 1rem;
            background: var(--off-white);
            border-radius: 8px;
        }
        
        .exercise-label {
            display: block;
            margin-bottom: 0.75rem;
            font-weight: bold;
        }
        
        /* Input Styles */
        .checkbox-group {
            display: flex;
            flex-wrap: wrap;
            gap: 0.75rem;
        }
        
        .checkbox-option {
            display: flex;
            align-items: center;
            gap: 0.5rem;
            padding: 0.5rem 1rem;
            background: white;
            border: 2px solid var(--sage-medium);
            border-radius: 8px;
            cursor: pointer;
            transition: all 0.3s ease;
        }
        
        .checkbox-option:hover {
            border-color: var(--dark-green);
            background: var(--sage-light);
        }
        
        .checkbox-option input {
            width: 18px;
            height: 18px;
            cursor: pointer;
        }
        
        .checkbox-option.correct {
            background: var(--success-light);
            border-color: var(--success);
        }
        
        .checkbox-option.incorrect {
            background: var(--error-light);
            border-color: var(--error);
        }
        
        .dropdown-select {
            padding: 0.75rem;
            font-size: 1rem;
            border: 2px solid var(--sage-medium);
            border-radius: 8px;
            background: white;
            min-width: 150px;
            cursor: pointer;
            font-family: inherit;
        }
        
        .dropdown-select:focus {
            outline: none;
            border-color: var(--dark-green);
        }
        
        .matching-row {
            display: flex;
            align-items: center;
            gap: 1rem;
            margin-bottom: 0.75rem;
            flex-wrap: wrap;
        }
        
        .matching-item {
            font-weight: bold;
            min-width: 40px;
            color: var(--dark-green);
            font-size: 1.2rem;
        }
        
        .radio-group {
            display: flex;
            gap: 1rem;
            flex-wrap: wrap;
        }
        
        .radio-option {
            display: flex;
            align-items: center;
            gap: 0.5rem;
            padding: 0.5rem 1rem;
            background: white;
            border: 2px solid var(--sage-medium);
            border-radius: 8px;
            cursor: pointer;
        }
        
        .radio-option:hover {
            border-color: var(--dark-green);
        }
        
        .radio-option input {
            width: 18px;
            height: 18px;
        }
        
        .radio-option.correct {
            background: var(--success-light);
            border-color: var(--success);
        }
        
        .radio-option.incorrect {
            background: var(--error-light);
            border-color: var(--error);
        }
        
        .true-false-group {
            display: flex;
            gap: 1rem;
        }
        
        .tf-btn {
            padding: 0.75rem 2rem;
            border: 2px solid var(--sage-medium);
            background: white;
            border-radius: 8px;
            cursor: pointer;
            font-weight: bold;
            transition: all 0.3s ease;
            font-family: inherit;
            font-size: 1rem;
        }
        
        .tf-btn:hover {
            border-color: var(--dark-green);
            background: var(--sage-light);
        }
        
        .tf-btn.selected {
            background: var(--dark-green);
            color: white;
            border-color: var(--dark-green);
        }
        
        .tf-btn.correct {
            background: var(--success);
            color: white;
            border-color: var(--success);
        }
        
        .tf-btn.incorrect {
            background: var(--error);
            color: white;
            border-color: var(--error);
        }
        
        .text-input {
            width: 100%;
            padding: 0.75rem;
            font-size: 1rem;
            border: 2px solid var(--sage-medium);
            border-radius: 8px;
            font-family: inherit;
            margin-bottom: 0.5rem;
        }
        
        .text-input:focus {
            outline: none;
            border-color: var(--dark-green);
        }
        
        .text-input.correct {
            background: var(--success-light);
            border-color: var(--success);
        }
        
        .text-input.incorrect {
            background: var(--error-light);
            border-color: var(--error);
        }
        
        .fill-blank {
            display: inline;
        }
        
        .fill-blank input {
            width: 200px;
            padding: 0.5rem;
            font-size: 1rem;
            border: 2px solid var(--sage-medium);
            border-radius: 4px;
            font-family: inherit;
            margin: 0 0.25rem;
        }
        
        .fill-blank input.correct {
            background: var(--success-light);
            border-color: var(--success);
        }
        
        .fill-blank input.incorrect {
            background: var(--error-light);
            border-color: var(--error);
        }
        
        textarea {
            width: 100%;
            min-height: 100px;
            padding: 0.75rem;
            font-size: 1rem;
            border: 2px solid var(--sage-medium);
            border-radius: 8px;
            font-family: inherit;
            resize: vertical;
        }
        
        textarea:focus {
            outline: none;
            border-color: var(--dark-green);
        }
        
        /* Feedback */
        .feedback {
            margin-top: 0.5rem;
            padding: 0.75rem;
            border-radius: 8px;
            font-size: 0.95rem;
            display: none;
        }
        
        .feedback.show {
            display: block;
        }
        
        .feedback.correct {
            background: var(--success-light);
            color: var(--success);
            border: 1px solid var(--success);
        }
        
        .feedback.incorrect {
            background: var(--error-light);
            color: var(--error);
            border: 1px solid var(--error);
        }
        
        .correct-answer {
            font-weight: bold;
            margin-top: 0.5rem;
        }
        
        /* Action Buttons */
        .action-buttons {
            display: flex;
            gap: 1rem;
            flex-wrap: wrap;
            justify-content: center;
            margin-top: 2rem;
            padding-top: 2rem;
            border-top: 2px solid var(--sage-medium);
        }
        
        .btn {
            padding: 1rem 2rem;
            font-size: 1rem;
            font-weight: bold;
            border: none;
            border-radius: 8px;
            cursor: pointer;
            transition: all 0.3s ease;
            font-family: inherit;
        }
        
        .btn-primary {
            background: var(--dark-green);
            color: white;
        }
        
        .btn-primary:hover {
            background: var(--text-dark);
            transform: translateY(-2px);
            box-shadow: 0 4px 12px rgba(0,0,0,0.2);
        }
        
        .btn-secondary {
            background: var(--beige);
            color: var(--text-dark);
            border: 2px solid var(--dark-green);
        }
        
        .btn-secondary:hover {
            background: var(--sage-light);
        }
        
        .btn-danger {
            background: var(--error-light);
            color: var(--error);
            border: 2px solid var(--error);
        }
        
        .btn-danger:hover {
            background: var(--error);
            color: white;
        }
        
        /* Footer */
        footer {
            background: var(--sage-light);
            border-top: 3px solid var(--dark-green);
            padding: 2rem 1rem;
            margin-top: 3rem;
        }
        
        .footer-content {
            max-width: 900px;
            margin: 0 auto;
            display: flex;
            justify-content: space-between;
            align-items: center;
            flex-wrap: wrap;
            gap: 1rem;
        }
        
        .footer-link {
            color: var(--dark-green);
            text-decoration: none;
            font-weight: bold;
            display: flex;
            align-items: center;
            gap: 0.5rem;
        }
        
        .footer-link:hover {
            text-decoration: underline;
        }
        
        /* Print Styles */
        @media print {
            header, .nav-bar, .action-buttons, .section-header, footer {
                display: none;
            }
            
            .section-content {
                display: block !important;
            }
            
            body {
                font-size: 12pt;
            }
            
            .exercises-section {
                border: 1px solid #000;
            }
        }
        
        /* Mobile Responsive */
        @media (max-width: 600px) {
            h1 {
                font-size: 1.5rem;
            }
            
            .header-content {
                flex-direction: column;
                text-align: center;
            }
            
            .nav-content {
                flex-direction: column;
                gap: 1rem;
            }
            
            .checkbox-group {
                flex-direction: column;
            }
            
            .matching-row {
                flex-direction: column;
                align-items: flex-start;
            }
            
            .action-buttons {
                flex-direction: column;
                width: 100%;
            }
            
            .btn {
                width: 100%;
            }
        }
        
        /* Smooth Scroll */
        html {
            scroll-behavior: smooth;
        }
        
        /* Focus States for Accessibility */
        button:focus,
        a:focus,
        input:focus,
        select:focus,
        textarea:focus {
            outline: 3px solid var(--warning);
            outline-offset: 2px;
        }
        
        /* Skip to content link */
        .skip-link {
            position: absolute;
            top: -40px;
            left: 0;
            background: var(--dark-green);
            color: white;
            padding: 8px;
            text-decoration: none;
            z-index: 1000;
        }
        
        .skip-link:focus {
            top: 0;
        }