:root {
    /* Light Mode Variables (Default) */
    --primary-background: #f8f9fa;
    --secondary-background: #fff;
    --tertiary-background: #e9ecef;
    --primary-text-color: #212529;
    --secondary-text-color: #343a40;
    --primary-purple-accent: #0a58ca;
    --primary-purple-hover: #0b5ed7;
    --primary-purple-active: #0a58ca;
    --primary-purple-text: #fff;
    --secondary-emerald-accent: #0f5132;
    --secondary-emerald-hover: #157347;
    --secondary-emerald-active: #146c43;
    --secondary-emerald-text: #fff;
    --highlight-gold-accent: #ffc107;
    --highlight-gold-text: #212529;
    --danger-red-accent: #dc3545;
    --danger-red-text: #fff;
    --focus-ring-color: #0d6efd;
    --card-shadow: 0 4px 8px rgba(0,0,0,0.1);
    --border-radius: 0.375rem;
    --bs-border-radius: var(--border-radius);
    --bs-body-font-family: 'Inter', 'Segoe UI', 'Roboto', 'Arial', sans-serif;
}
.dark-mode {
    /* Dark Mode Variables (Override) */
    --primary-background: #000000;
    --secondary-background: #121212;
    --tertiary-background: #222222;
    --primary-text-color: #F0F0F0;
    --secondary-text-color: #C0C0C0;
    --primary-purple-accent: #8E24AA;
    --primary-purple-hover: #7A1F97;
    --primary-purple-active: #6B1B82;
    --primary-purple-text: #F0F0F0;
    --secondary-emerald-accent: #00695C;
    --secondary-emerald-hover: #005c50;
    --secondary-emerald-active: #004d43;
    --secondary-emerald-text: #F0F0F0;
    --highlight-gold-accent: #FFCA28;
    --highlight-gold-text: #1A1A1A;
    --danger-red-accent: #C62828;
    --danger-red-text: #F0F0F0;
    --focus-ring-color: #FFCA28;
    --card-shadow: 0 4px 8px rgba(0,0,0,0.2);
}
/* Specific Dark Mode Overrides */
.dark-mode .text-muted,
.dark-mode .form-text,
.dark-mode small,
.dark-mode .progress-label,
.dark-mode .card-title,
.dark-mode label,
.dark-mode .form-label {
    color: var(--secondary-text-color) !important;
    opacity: 1 !important;
}

html, body, .dark-mode html, .dark-mode body {
    background: var(--primary-background) !important;
    color: var(--primary-text-color);
    font-family: var(--bs-body-font-family);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}
/* Mobile Physics: Prevent double-tap zoom on interactive elements */
a, .btn, .choice-btn, input, select, textarea, button, label {
    touch-action: manipulation;
}
body {
    min-height: 100vh;
}
.quiz-container {
    max-width: 800px;
    margin: 2rem auto;
    padding: 1rem;
}
.card {
    background: var(--secondary-background);
    color: var(--primary-text-color);
    border-radius: var(--border-radius);
    box-shadow: var(--card-shadow);
    border: none;
}
.score-display {
    background: var(--tertiary-background);
    color: var(--primary-text-color);
    border-radius: var(--border-radius);
    padding: 10px 15px;
    text-align: center;
    min-width: 220px;
    border: 1px solid var(--secondary-background);
}
.progress-container {
    display: flex;
    align-items: center;
    gap: 15px;
    margin-bottom: 20px;
}
.progress-label {
    font-weight: 600;
    color: var(--secondary-text-color);
}
.progress {
    background: var(--tertiary-background);
    border-radius: 6px;
}
.progress-bar {
    background: var(--primary-purple-accent);
    color: var(--primary-purple-text);
    font-weight: 600;
    transition: transform 0.5s;
    transform-origin: left;
    will-change: transform;
}
.divider-text {
    text-align: center;
    margin: 1rem 0;
    font-weight: 500;
    color: var(--secondary-text-color);
}
.explanation-box {
    background: var(--tertiary-background);
    border-radius: var(--border-radius);
    padding: 15px;
    margin-top: 20px;
    color: var(--primary-text-color);
    box-shadow: var(--card-shadow);
}
.choice-btn {
    background: var(--secondary-background);
    color: var(--primary-text-color);
    border: 1px solid var(--tertiary-background);
    border-radius: var(--border-radius);
    text-align: left !important;
    padding: 0.75rem 1rem !important;
    font-weight: 500;
    transition: all 0.2s ease-in-out;
    outline: none;
    touch-action: manipulation;
    white-space: normal;
    word-wrap: break-word;
}
.choice-btn:hover:not(:disabled) {
    background: var(--primary-purple-hover);
    color: var(--primary-purple-text);
    transform: translateY(-2px) scale(1.01);
}
.choice-btn:active {
    background: var(--primary-purple-active);
    color: var(--primary-purple-text);
}
.choice-btn:focus-visible {
    outline: 2.5px solid var(--focus-ring-color);
    outline-offset: 2px;
    box-shadow: 0 0 0 3px var(--focus-ring-color);
}
.choice-btn.correct-answer {
    background: var(--secondary-emerald-accent);
    color: var(--secondary-emerald-text);
    border-color: var(--secondary-emerald-accent);
}
.choice-btn.incorrect-answer {
    background: var(--danger-red-accent);
    color: var(--danger-red-text);
    border-color: var(--danger-red-accent);
}
.choice-btn.user-selected.incorrect-answer {
    opacity: 0.7;
}
.btn {
    font-weight: 600;
    border-radius: var(--border-radius);
    letter-spacing: 0.02em;
    transition: all 0.2s;
    outline: none;
    touch-action: manipulation;
    white-space: normal;
    overflow-wrap: break-word;
}
.btn-primary {
    background: var(--primary-purple-accent);
    border-color: var(--primary-purple-accent);
    color: var(--primary-purple-text);
}
.btn-primary:hover, .btn-primary:focus {
    background: var(--primary-purple-hover);
    border-color: var(--primary-purple-hover);
    color: var(--primary-purple-text);
}
.btn-primary:active {
    background: var(--primary-purple-active);
    border-color: var(--primary-purple-active);
}
.btn-success {
    background: var(--secondary-emerald-accent);
    border-color: var(--secondary-emerald-accent);
    color: var(--secondary-emerald-text);
}
.btn-success:hover, .btn-success:focus {
    background: var(--secondary-emerald-hover);
    border-color: var(--secondary-emerald-hover);
}
.btn-success:active {
    background: var(--secondary-emerald-active);
    border-color: var(--secondary-emerald-active);
}
.btn-info {
    background: var(--highlight-gold-accent);
    border-color: var(--highlight-gold-accent);
    color: var(--highlight-gold-text);
}
.btn-info:hover, .btn-info:focus {
    background: #ffd95a;
    border-color: #ffd95a;
    color: var(--highlight-gold-text);
}
.btn-info:active {
    background: #e6b800;
    border-color: #e6b800;
}
.btn-danger {
    background: var(--danger-red-accent);
    border-color: var(--danger-red-accent);
    color: var(--danger-red-text);
}
.btn-danger:hover, .btn-danger:focus {
    background: #b71c1c;
    border-color: #b71c1c;
}
.btn-danger:active {
    background: #8b1818;
    border-color: #8b1818;
}
.loading-spinner {
    border: 4px solid var(--tertiary-background);
    border-top: 4px solid var(--primary-purple-accent);
    border-radius: 50%;
    width: 30px;
    height: 30px;
    animation: spin 1s linear infinite;
    margin: 20px auto;
}
@keyframes spin { 0% { transform: rotate(0deg); } 100% { transform: rotate(360deg); } }
.d-none { display: none !important; }
/* Scrollbar styling for WebKit browsers */
::-webkit-scrollbar {
    width: 10px;
    background: var(--secondary-background);
}
::-webkit-scrollbar-thumb {
    background: var(--secondary-text-color);
    border-radius: 6px;
}
::-webkit-scrollbar-thumb:hover {
    background: var(--primary-purple-accent);
}
/* Headings and typography */
h1, h2, h3, h4, h5, h6 {
    color: var(--primary-text-color);
    font-weight: 700;
    letter-spacing: 0.02em;
}
.card-title, label, .form-label, .form-text, small, .progress-label {
    color: var(--secondary-text-color);
}
.text-muted, small, .form-text {
    color: var(--secondary-text-color) !important;
    opacity: 1 !important;
}
/* Accessibility: focus ring for all interactive elements */
button:focus-visible, input:focus-visible, select:focus-visible, textarea:focus-visible {
    outline: 2.5px solid var(--focus-ring-color) !important;
    outline-offset: 2px !important;
    box-shadow: 0 0 0 3px var(--focus-ring-color) !important;
}
/* Animation for fade-in */
.fade-in { animation: fadeInAnimation 0.2s ease-in; }
@keyframes fadeInAnimation { from { opacity: 0; transform: translateY(10px); } to { opacity: 1; transform: translateY(0); } }

/* Theme Toggle Styles */
/* Default (Light) */
#themeToggleBtn .bi {
    color: var(--primary-purple-accent) !important;
    transition: color 0.2s;
}
#themeToggleBtn {
    background: var(--secondary-background) !important;
    border: 1.5px solid var(--primary-purple-accent) !important;
}

/* Dark Mode Override */
.dark-mode #themeToggleBtn .bi {
    color: var(--highlight-gold-accent) !important;
}
.dark-mode #themeToggleBtn {
    background: var(--secondary-background) !important;
    border: 1.5px solid var(--highlight-gold-accent) !important;
}

#themeToggleBtn:focus-visible {
    outline: 2.5px solid var(--focus-ring-color) !important;
    outline-offset: 2px !important;
    box-shadow: 0 0 0 3px var(--focus-ring-color) !important;
}

/* Accessibility overrides for text colors to ensure WCAG AA compliance */
/* Default (Light Mode) */
.text-success { color: #146c43 !important; }
.text-danger { color: #b02a37 !important; }

/* Dark Mode Overrides */
.dark-mode .text-success { color: #66BB6A !important; }
.dark-mode .text-danger { color: #EF9A9A !important; }

/* Bolt Optimization: Virtualize rendering for long review lists */
.review-card {
    content-visibility: auto;
    contain-intrinsic-size: 1px 300px;
}
.hidden-by-filter {
    display: none !important;
}
/* Reduced Motion */
@media (prefers-reduced-motion: reduce) {
    *, ::before, ::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }
}

/* --- Extracted Inline Styles --- */

.bg-transparent {
    background: transparent !important;
}
#themeToggleBtn {
    min-width: 44px;
}
#iconSun {
    font-size: 1.5rem;
    display: inline;
}
#iconMoon {
    font-size: 1.5rem;
    display: none;
}
.dark-mode #iconSun {
    display: none;
}
.dark-mode #iconMoon {
    display: inline;
}
.progress-sm {
    height: 10px;
}
.progress-lg {
    height: 25px;
}
#progressBar {
    width: 100%;
    transform: scaleX(0);
}
#finalPercentageBar {
    width: 100%;
    transform: scaleX(0);
}
#finalPercentageText {
    top: 0;
    left: 0;
    font-weight: 600;
    color: var(--primary-purple-text);
    pointer-events: none;
}

/* Print Support */
@media print {
    /* Reset colors for ink saving */
    body, .card, .score-display, .explanation-box, .review-card {
        background: #ffffff !important;
        color: #000000 !important;
        box-shadow: none !important;
        border: 1px solid #ddd !important;
    }

    /* Hide navigation and controls */
    header.d-flex,
    #themeToggleBtn,
    .btn,
    #uploadSection,
    .progress-container,
    #reviewFilterControls,
    footer {
        display: none !important;
    }

    /* Ensure review cards don't break awkwardly */
    .review-card {
        break-inside: avoid;
        page-break-inside: avoid;
        margin-bottom: 20px;
        content-visibility: visible !important;
        contain-intrinsic-size: auto !important;
    }

    /* Expand containers */
    .quiz-container {
        max-width: 100% !important;
        margin: 0 !important;
        padding: 0 !important;
    }
}