/* ===== CSS Variables ===== */
:root {
    --primary-color: #6366f1;
    --primary-dark: #4f46e5;
    --success-color: #22c55e;
    --success-bg: #dcfce7;
    --error-color: #ef4444;
    --error-bg: #fee2e2;
    --warning-color: #f59e0b;
    --bg-color: #f8fafc;
    --card-bg: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --transition: all 0.3s ease;
}

/* ===== Reset & Base Styles ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

/* ===== Index Page Styles ===== */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
.header {
    text-align: center;
    padding: 40px 20px;
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    border-radius: var(--radius-lg);
    margin-bottom: 40px;
    box-shadow: var(--shadow-lg);
}

.header-content {
    color: white;
}

.university-name {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 10px;
    text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.2);
}

.subtitle {
    font-size: 1.5rem;
    font-weight: 400;
    opacity: 0.95;
}

/* Main Content */
.main-content {
    flex: 1;
}

.section-title {
    font-size: 1.5rem;
    color: var(--text-primary);
    margin-bottom: 24px;
    text-align: center;
}

/* Quiz Grid */
.quiz-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 24px;
    padding: 10px;
}

/* Quiz Card */
.quiz-card {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    overflow: hidden;
    transition: var(--transition);
    cursor: pointer;
    text-decoration: none;
    color: inherit;
    display: flex;
    flex-direction: column;
}

.quiz-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.quiz-card-thumbnail {
    height: 180px;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

.quiz-card-thumbnail svg {
    width: 100px;
    height: 100px;
    opacity: 0.9;
}

.quiz-card-content {
    padding: 20px;
    border-top: 1px solid var(--border-color);
}

.quiz-card-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 8px;
}

.quiz-card-desc {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 12px;
}

.quiz-card-stats {
    display: flex;
    justify-content: space-between;
    font-size: 0.85rem;
    color: var(--text-secondary);
}

.quiz-card-stats span {
    display: flex;
    align-items: center;
    gap: 5px;
}

/* Footer */
.footer {
    text-align: center;
    padding: 30px;
    margin-top: 40px;
    border-top: 1px solid var(--border-color);
}

.footer p {
    font-size: 1rem;
    color: var(--text-secondary);
}

.heart {
    color: #ef4444;
    animation: heartbeat 1.5s infinite;
}

@keyframes heartbeat {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.1); }
}

/* ===== Quiz Page Styles ===== */
.quiz-page {
    background: var(--bg-color);
}

.quiz-container {
    display: flex;
    min-height: 100vh;
}

/* Mobile Menu Button */
.mobile-menu-btn {
    display: none;
    position: fixed;
    bottom: 20px;
    right: 20px;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: 50px;
    padding: 12px 20px;
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    z-index: 100;
    box-shadow: var(--shadow-lg);
    align-items: center;
    gap: 8px;
    transition: var(--transition);
}

.mobile-menu-btn:hover {
    background: var(--primary-dark);
}

.mobile-menu-btn svg {
    width: 20px;
    height: 20px;
}

/* Sidebar */
.sidebar {
    width: 320px;
    background: var(--card-bg);
    border-right: 1px solid var(--border-color);
    padding: 20px;
    display: flex;
    flex-direction: column;
    height: 100vh;
    position: sticky;
    top: 0;
    overflow-y: auto;
}

.sidebar-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    padding-bottom: 15px;
    border-bottom: 1px solid var(--border-color);
}

.sidebar-header h3 {
    font-size: 1.25rem;
    color: var(--text-primary);
}

.close-sidebar {
    display: none;
    background: none;
    border: none;
    cursor: pointer;
    padding: 5px;
    color: var(--text-secondary);
}

.close-sidebar svg {
    width: 24px;
    height: 24px;
}

/* Progress Stats */
.progress-stats {
    display: flex;
    justify-content: space-between;
    margin-bottom: 15px;
    gap: 10px;
}

.stat {
    flex: 1;
    text-align: center;
    padding: 12px 8px;
    background: var(--bg-color);
    border-radius: var(--radius-sm);
}

.stat-value {
    display: block;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

.stat:nth-child(2) .stat-value {
    color: var(--success-color);
}

.stat:nth-child(3) .stat-value {
    color: var(--error-color);
}

.stat-label {
    font-size: 0.75rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

/* Progress Bar */
.progress-bar-container {
    height: 8px;
    background: var(--bg-color);
    border-radius: 4px;
    margin-bottom: 20px;
    overflow: hidden;
}

.progress-bar {
    height: 100%;
    background: linear-gradient(90deg, var(--primary-color), var(--success-color));
    border-radius: 4px;
    width: 0%;
    transition: width 0.5s ease;
}

/* Question Navigation */
.question-nav {
    flex: 1;
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 8px;
    align-content: start;
    overflow-y: auto;
    padding: 5px;
    margin-bottom: 20px;
}

.q-nav-btn {
    width: 100%;
    aspect-ratio: 1;
    border: 2px solid var(--border-color);
    background: var(--card-bg);
    border-radius: var(--radius-sm);
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    color: var(--text-primary);
}

.q-nav-btn:hover {
    border-color: var(--primary-color);
    background: rgba(99, 102, 241, 0.1);
}

.q-nav-btn.active {
    background: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
}

.q-nav-btn.correct {
    background: var(--success-bg);
    border-color: var(--success-color);
    color: var(--success-color);
}

.q-nav-btn.incorrect {
    background: var(--error-bg);
    border-color: var(--error-color);
    color: var(--error-color);
}

.q-nav-btn.skipped {
    background: #fef3c7;
    border-color: var(--warning-color);
    color: var(--warning-color);
}

/* Sidebar Actions */
.sidebar-actions {
    display: flex;
    flex-direction: column;
    gap: 10px;
    padding-top: 15px;
    border-top: 1px solid var(--border-color);
}

/* Sidebar Overlay */
.sidebar-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.5);
    z-index: 199;
}

/* Main Quiz Area */
.quiz-main {
    flex: 1;
    padding: 30px;
    max-width: 900px;
    margin: 0 auto;
}

.quiz-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 30px;
}

.back-link {
    display: flex;
    align-items: center;
    gap: 8px;
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
}

.back-link:hover {
    color: var(--primary-color);
}

.back-link svg {
    width: 20px;
    height: 20px;
}

.quiz-info {
    font-size: 1rem;
    color: var(--text-secondary);
    font-weight: 600;
}

/* Question Card */
.question-card {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    padding: 30px;
    box-shadow: var(--shadow-md);
    margin-bottom: 24px;
}

.question-number {
    display: inline-block;
    background: var(--primary-color);
    color: white;
    padding: 6px 14px;
    border-radius: 20px;
    font-size: 0.85rem;
    font-weight: 600;
    margin-bottom: 20px;
}

.question-text {
    font-size: 1.25rem;
    line-height: 1.7;
    color: var(--text-primary);
    margin-bottom: 25px;
}

/* Options */
.options-container {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.option {
    display: flex;
    align-items: flex-start;
    padding: 16px 20px;
    background: var(--bg-color);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: var(--transition);
    gap: 15px;
}

.option:hover:not(.disabled) {
    border-color: var(--primary-color);
    background: rgba(99, 102, 241, 0.05);
}

.option.selected {
    border-color: var(--primary-color);
    background: rgba(99, 102, 241, 0.1);
}

.option.correct {
    border-color: var(--success-color);
    background: var(--success-bg);
}

.option.incorrect {
    border-color: var(--error-color);
    background: var(--error-bg);
}

.option.disabled {
    cursor: default;
}

.option-label {
    width: 32px;
    height: 32px;
    min-width: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: white;
    border: 2px solid var(--border-color);
    border-radius: 50%;
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--text-secondary);
    transition: var(--transition);
}

.option.selected .option-label {
    background: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
}

.option.correct .option-label {
    background: var(--success-color);
    border-color: var(--success-color);
    color: white;
}

.option.incorrect .option-label {
    background: var(--error-color);
    border-color: var(--error-color);
    color: white;
}

.option-text {
    flex: 1;
    font-size: 1rem;
    line-height: 1.5;
    padding-top: 4px;
}

/* Question Actions */
.question-actions {
    margin-top: 20px;
    padding-top: 20px;
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: center;
}

/* Navigation Buttons */
.navigation-buttons {
    display: flex;
    justify-content: space-between;
    gap: 15px;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px 24px;
    border: none;
    border-radius: var(--radius-sm);
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    text-decoration: none;
}

.btn svg {
    width: 18px;
    height: 18px;
}

.btn-nav {
    background: var(--card-bg);
    color: var(--text-primary);
    border: 2px solid var(--border-color);
    flex: 1;
}

.btn-nav:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
}

.btn-nav.btn-primary {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

.btn-nav.btn-primary:hover {
    background: var(--primary-dark);
    border-color: var(--primary-dark);
}

.btn-show-answer {
    background: transparent;
    color: var(--primary-color);
    border: 2px solid var(--primary-color);
}

.btn-show-answer:hover {
    background: var(--primary-color);
    color: white;
}

.btn-reset {
    background: var(--error-bg);
    color: var(--error-color);
    border: 2px solid var(--error-color);
}

.btn-reset:hover {
    background: var(--error-color);
    color: white;
}

.btn-home {
    background: var(--bg-color);
    color: var(--text-primary);
    border: 2px solid var(--border-color);
}

.btn-home:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
}

/* ===== Responsive Styles ===== */
@media (max-width: 1024px) {
    .quiz-main {
        padding: 20px;
    }
}

@media (max-width: 768px) {
    /* Index Page */
    .header {
        padding: 30px 15px;
    }

    .university-name {
        font-size: 1.8rem;
    }

    .subtitle {
        font-size: 1.2rem;
    }

    .quiz-grid {
        grid-template-columns: 1fr;
    }

    .quiz-card {
        flex-direction: row;
    }

    .quiz-card-thumbnail {
        width: 120px;
        height: auto;
        min-height: 120px;
    }

    .quiz-card-thumbnail svg {
        width: 60px;
        height: 60px;
    }

    .quiz-card-content {
        border-top: none;
        border-left: 1px solid var(--border-color);
        flex: 1;
    }

    /* Quiz Page */
    .mobile-menu-btn {
        display: flex;
    }

    .sidebar {
        position: fixed;
        left: -100%;
        top: 0;
        height: 100vh;
        z-index: 200;
        width: 300px;
        transition: left 0.3s ease;
    }

    .sidebar.open {
        left: 0;
    }

    .sidebar-overlay.open {
        display: block;
    }

    .close-sidebar {
        display: block;
    }

    .quiz-main {
        padding: 15px;
        padding-bottom: 80px;
    }

    .question-card {
        padding: 20px;
    }

    .question-text {
        font-size: 1.1rem;
    }

    .option {
        padding: 12px 15px;
    }

    .option-label {
        width: 28px;
        height: 28px;
        min-width: 28px;
        font-size: 0.85rem;
    }

    .navigation-buttons {
        flex-direction: column;
    }

    .btn-nav {
        width: 100%;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 10px;
    }

    .university-name {
        font-size: 1.5rem;
    }

    .subtitle {
        font-size: 1rem;
    }

    .quiz-card-thumbnail {
        width: 100px;
    }

    .quiz-card-title {
        font-size: 1.1rem;
    }

    .progress-stats {
        gap: 5px;
    }

    .stat {
        padding: 8px 5px;
    }

    .stat-value {
        font-size: 1.2rem;
    }

    .question-nav {
        grid-template-columns: repeat(5, 1fr);
        gap: 6px;
    }

    .q-nav-btn {
        font-size: 0.75rem;
    }
}

/* ===== Scrollbar Styling ===== */
::-webkit-scrollbar {
    width: 8px;
}

::-webkit-scrollbar-track {
    background: var(--bg-color);
}

::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--text-secondary);
}

/* ===== Loading State ===== */
.loading {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 300px;
    color: var(--text-secondary);
}

.spinner {
    width: 40px;
    height: 40px;
    border: 3px solid var(--border-color);
    border-top-color: var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin-bottom: 15px;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}