.serbian-a1-book-container {

    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;

    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);

    min-height: 100vh;

    display: flex;

}



/* Sidebar */

.serbian-a1-sidebar {

    width: 280px;

    background: white;

    padding: 20px;

    overflow-y: auto;

    box-shadow: 2px 0 10px rgba(0,0,0,0.1);

}



.serbian-a1-sidebar .logo {

    text-align: center;

    margin-bottom: 20px;

    padding-bottom: 20px;

    border-bottom: 2px solid #667eea;

}



.serbian-a1-sidebar .logo h1 {

    color: #667eea;

    font-size: 1.5em;

    margin-bottom: 5px;

    margin-top: 0;

}



.serbian-a1-sidebar .logo p {

    color: #666;

    font-size: 0.9em;

    margin: 0;

}



.language-selector {

    margin-bottom: 20px;

    padding: 15px;

    background: #f8f9fa;

    border-radius: 10px;

}



.language-selector label {

    display: block;

    margin-bottom: 8px;

    font-weight: bold;

    color: #667eea;

}



.language-select {

    width: 100%;

    padding: 10px;

    border: 2px solid #667eea;

    border-radius: 8px;

    font-size: 1em;

    cursor: pointer;

    background: white;

}



.lessons-list {

    list-style: none;

    padding: 0;

    margin: 0;

}



.lesson-item {

    padding: 12px 15px;

    margin-bottom: 8px;

    background: #f8f9fa;

    border-radius: 8px;

    cursor: pointer;

    transition: all 0.3s;

    border-left: 4px solid transparent;

}



.lesson-item:hover {

    background: #e9ecef;

    border-left-color: #667eea;

}



.lesson-item.active {

    background: #667eea;

    color: white;

    border-left-color: #764ba2;

    font-weight: bold;

}



.lesson-number {

    font-size: 0.85em;

    opacity: 0.8;

}



/* Main Content */

.serbian-a1-content {

    flex: 1;

    padding: 40px;

    overflow-y: auto;

}



.lesson-content {

    background: white;

    padding: 40px;

    border-radius: 20px;

    box-shadow: 0 10px 40px rgba(0,0,0,0.1);

    animation: fadeIn 0.5s;

}



@keyframes fadeIn {

    from { 

        opacity: 0; 

        transform: translateY(20px); 

    }

    to { 

        opacity: 1; 

        transform: translateY(0); 

    }

}



.lesson-header {

    margin-bottom: 30px;

    padding-bottom: 20px;

    border-bottom: 3px solid #667eea;

}



.lesson-title {

    color: #667eea;

    font-size: 2em;

    margin: 0 0 10px 0;

}



.section {

    margin-bottom: 40px;

}



.section-title {

    color: #764ba2;

    font-size: 1.5em;

    margin-bottom: 15px;

    padding-left: 15px;

    border-left: 5px solid #764ba2;

}



/*intro*/

.intro-box {

    background: #e7f3ff;

    border-left: 5px solid #2196F3;

    padding: 20px;

    margin: 20px 0;

    border-radius: 10px;

    line-height: 1.8;

}



.intro-box h4 {

    color: #1976D2;

    margin-top: 0;

}



/* Vocabulary Table */

.vocab-table {

    width: 100%;

    border-collapse: collapse;

    margin: 20px 0;

    background: #f8f9fa;

    border-radius: 10px;

    overflow: hidden;

}



.vocab-table th {

    background: #667eea;

    color: white;

    padding: 15px;

    text-align: left;

    font-weight: bold;

}



.vocab-table td {

    padding: 12px 15px;

    border-bottom: 1px solid #dee2e6;

}



.vocab-table tr:last-child td {

    border-bottom: none;

}



.vocab-table tr:hover {

    background: #e9ecef;

}



/* Grammar Box */

.grammar-box {

    background: #fff3cd;

    border-left: 5px solid #ffc107;

    padding: 20px;

    margin: 20px 0;

    border-radius: 10px;

}



.grammar-box h4 {

    color: #856404;

    margin-top: 0;

    margin-bottom: 10px;

}



.grammar-box ul,

.grammar-box ol {

    margin-left: 25px;

    line-height: 1.8;

}



.grammar-box li {

    margin-bottom: 8px;

}



/* Dialogue */

.dialogue {

    background: #f8f9fa;

    padding: 20px;

    border-radius: 10px;

    margin: 20px 0;

}



.dialogue-line {

    margin-bottom: 15px;

    padding: 10px;

    background: white;

    border-radius: 8px;

}



.translation {

    color: #666;

    font-style: italic;

    font-size: 0.9em;

    margin-top: 5px;

}



/* Exercises */

.exercise {

    background: #f8f9fa;

    padding: 25px;

    border-radius: 15px;

    margin-bottom: 20px;

    border-left: 5px solid #667eea;

}



.exercise-question {

    font-size: 1.1em;

    margin-bottom: 15px;

    color: #333;

    font-weight: 500;

}



.exercise-input,

.translation-input {

    width: 100%;

    padding: 12px;

    border: 2px solid #667eea;

    border-radius: 8px;

    font-size: 1em;

    margin-bottom: 10px;

    font-family: inherit;

}



.exercise-options {

    display: flex;

    flex-direction: column;

    gap: 10px;

    margin-bottom: 15px;

}



.option-btn {

    padding: 12px 20px;

    border: 2px solid #e0e0e0;

    background: white;

    border-radius: 8px;

    cursor: pointer;

    transition: all 0.3s;

    text-align: left;

    font-size: 1em;

    color: #333!important;

}



.option-btn:hover {

    border-color: #667eea;

    background: #f8f9fa;

    color: grey;

}



.option-btn.selected {

    border-color: #667eea;

    background: #e7f0ff;

}



.option-btn.correct {

    border-color: #28a745;

    background: #d4edda;

    color: #155724;

}



.option-btn.incorrect {

    border-color: #dc3545;

    background: #f8d7da;

    color: #721c24;

}



.check-btn,

.reset-btn {

    background: #667eea;

    color: white;

    border: none;

    padding: 12px 30px;

    border-radius: 25px;

    font-size: 1em;

    cursor: pointer;

    margin-top: 10px;

    margin-right: 10px;

    font-weight: bold;

    transition: all 0.3s;

}



.check-btn:hover,

.reset-btn:hover {

    background: #764ba2;

    transform: translateY(-2px);

}



.reset-btn {

    background: #6c757d;

}



.reset-btn:hover {

    background: #5a6268;

}



.feedback {

    margin-top: 15px;

}



.feedback-content {

    padding: 15px;

    border-radius: 8px;

    font-weight: bold;

}



.feedback-content.correct {

    background: #d4edda;

    color: #155724;

}



.feedback-content.incorrect {

    background: #f8d7da;

    color: #721c24;

}



/* Match Exercise */

.match-container {

    margin: 20px 0;

}



.match-item {

    display: flex;

    align-items: center;

    gap: 15px;

    padding: 12px;

    margin-bottom: 10px;

    background: white;

    border-radius: 8px;

}



.match-item.correct {

    background: #d4edda;

}



.match-item.incorrect {

    background: #f8d7da;

}



.match-select {

    padding: 8px;

    border: 2px solid #667eea;

    border-radius: 5px;

    font-size: 1em;

}



/* Ordering Exercise */

.ordering-container {

    margin: 20px 0;

}



.ordering-item {

    display: flex;

    align-items: center;

    gap: 10px;

    padding: 12px;

    margin-bottom: 8px;

    background: white;

    border-radius: 8px;

    cursor: move;

    transition: all 0.3s;

}



.ordering-item:hover {

    background: #e7f0ff;

}



.ordering-item.dragging {

    opacity: 0.5;

}



.drag-handle {

    color: #999;

    font-size: 18px;

    user-select: none;

}



/* Navigation Buttons */

.nav-buttons {

    display: flex;

    justify-content: space-between;

    margin-top: 40px;

    padding-top: 20px;

    border-top: 2px solid #e0e0e0;

}



.nav-btn {

    padding: 12px 30px;

    border: none;

    border-radius: 25px;

    font-size: 1em;

    cursor: pointer;

    font-weight: bold;

    transition: all 0.3s;

}



.nav-btn.prev {

    background: #6c757d;

    color: white;

}



.nav-btn.next {

    background: #667eea;

    color: white;

}



.nav-btn:hover:not(:disabled) {

    transform: translateY(-2px);

    box-shadow: 0 5px 15px rgba(0,0,0,0.2);

}



.nav-btn:disabled {

    opacity: 0.5;

    cursor: not-allowed;

}



/* Responsive */

@media (max-width: 768px) {

    .serbian-a1-book-container {

        flex-direction: column;

    }

    

    .serbian-a1-sidebar {

        width: 100%;

        max-height: 300px;

    }

    

    .serbian-a1-content {

        padding: 20px;

    }

    

    .lesson-content {

        padding: 20px;

    }

    

    .lesson-title {

        font-size: 1.5em;

    }

}