/* ========================================
   Fraction & Decimal Explorer - Styles
   "Neon Cosmos" Theme - Vibrant & Playful
   ======================================== */

:root {
    /* Color Palette - Neon Cosmos */
    --primary: #a78bfa;
    --primary-light: #c4b5fd;
    --primary-dark: #7c3aed;
    --secondary: #fb923c;
    --secondary-light: #fdba74;
    --accent-pink: #f472b6;
    --accent-green: #34d399;
    --accent-cyan: #22d3ee;
    --accent-purple: #c084fc;
    --accent-blue: #60a5fa;

    /* Backgrounds */
    --bg-main: #0c0a1a;
    --bg-card: #16132a;
    --bg-card-hover: #1f1b38;
    --bg-input: #110e22;

    /* Text */
    --text-primary: #eef2ff;
    --text-secondary: #a5b4cf;
    --text-muted: #6b7a96;

    /* Gradients */
    --gradient-primary: linear-gradient(135deg, #a78bfa 0%, #f472b6 100%);
    --gradient-success: linear-gradient(135deg, #34d399 0%, #22d3ee 100%);
    --gradient-warning: linear-gradient(135deg, #fb923c 0%, #f472b6 100%);
    --gradient-fun: linear-gradient(135deg, #f472b6 0%, #a78bfa 100%);
    --gradient-cosmic: linear-gradient(135deg, #6366f1 0%, #a78bfa 50%, #f472b6 100%);

    /* Shadows */
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.4);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.5);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.6);
    --shadow-glow: 0 0 24px rgba(167, 139, 250, 0.35);
    --shadow-glow-pink: 0 0 24px rgba(244, 114, 182, 0.3);

    /* Spacing */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-full: 9999px;

    /* Transitions */
    --transition-fast: 0.15s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
}

/* Reset */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: 'Nunito', system-ui, -apple-system, sans-serif;
    background: var(--bg-main);
    color: var(--text-primary);
    min-height: 100vh;
    line-height: 1.5;
    overflow-x: hidden;
}

/* Cosmic Background */
body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background:
        radial-gradient(ellipse at 15% 85%, rgba(167, 139, 250, 0.12) 0%, transparent 50%),
        radial-gradient(ellipse at 85% 15%, rgba(244, 114, 182, 0.1) 0%, transparent 50%),
        radial-gradient(ellipse at 50% 50%, rgba(34, 211, 238, 0.05) 0%, transparent 40%);
    pointer-events: none;
    z-index: -1;
}

/* App Container */
.app-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 10px 14px;
}

/* ========================================
   Header
   ======================================== */

.app-header {
    background: rgba(22, 19, 42, 0.85);
    backdrop-filter: blur(20px);
    border-radius: var(--radius-lg);
    padding: 10px 16px;
    margin-bottom: 8px;
    border: 1px solid rgba(167, 139, 250, 0.15);
    box-shadow: var(--shadow-sm);
}

.header-row {
    display: flex;
    align-items: center;
    gap: 16px;
    flex-wrap: wrap;
}

.logo {
    display: flex;
    align-items: center;
    gap: 8px;
    flex-shrink: 0;
}

.logo-icon {
    font-size: 1.4rem;
}

.logo h1 {
    font-size: 1.2rem;
    font-weight: 800;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    white-space: nowrap;
}

.nav-tabs {
    display: flex;
    gap: 4px;
    flex-wrap: wrap;
    flex: 1;
}

.nav-tab {
    background: transparent;
    border: 1.5px solid transparent;
    color: var(--text-secondary);
    padding: 6px 14px;
    border-radius: var(--radius-full);
    font-family: inherit;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
    white-space: nowrap;
}

.nav-tab:hover {
    background: rgba(167, 139, 250, 0.1);
    color: var(--text-primary);
}

.nav-tab.active {
    background: var(--gradient-primary);
    color: white;
    box-shadow: var(--shadow-glow);
}

/* ========================================
   Mascot Tip Bar (inline)
   ======================================== */

.mascot-bar {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 8px;
    padding: 0 4px;
    min-height: 32px;
}

.mascot-toggle {
    display: flex;
    align-items: center;
    gap: 4px;
    background: rgba(167, 139, 250, 0.15);
    border: 1px solid rgba(167, 139, 250, 0.25);
    color: var(--primary-light);
    padding: 4px 10px;
    border-radius: var(--radius-full);
    font-family: inherit;
    font-size: 0.8rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
    flex-shrink: 0;
}

.mascot-toggle:hover {
    background: rgba(167, 139, 250, 0.25);
}

.mascot-icon {
    font-size: 1rem;
}

.mascot-bubble {
    flex: 1;
    overflow: hidden;
    max-height: 0;
    opacity: 0;
    transition: max-height 0.3s ease, opacity 0.2s ease;
}

.mascot-bubble.show {
    max-height: 60px;
    opacity: 1;
}

.mascot-bubble p {
    font-size: 0.85rem;
    color: var(--text-secondary);
    line-height: 1.3;
}

/* ========================================
   Main Content & Tabs
   ======================================== */

.tab-content {
    display: none;
    animation: fadeIn 0.3s ease;
}

.tab-content.active {
    display: block;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.section-header {
    text-align: center;
    margin-bottom: 14px;
}

.section-header h2 {
    font-size: 1.4rem;
    font-weight: 800;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.subtitle {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-top: 2px;
}

/* ========================================
   Fraction Input
   ======================================== */

.input-group {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 16px;
    margin-bottom: 16px;
    flex-wrap: wrap;
}

.fraction-builder {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 3px;
}

.fraction-builder.small {
    transform: scale(0.8);
}

.fraction-part {
    width: 80px;
    height: 46px;
    background: var(--bg-card);
    border: 2px solid var(--primary);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-size: 1.5rem;
    font-weight: 700;
    text-align: center;
    font-family: inherit;
    transition: all var(--transition-fast);
}

.fraction-part:focus {
    outline: none;
    border-color: var(--secondary);
    box-shadow: 0 0 16px rgba(251, 146, 60, 0.3);
}

.fraction-line {
    width: 96px;
    height: 4px;
    background: var(--gradient-primary);
    border-radius: var(--radius-full);
}

.equals {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-muted);
}

.decimal-display {
    font-size: 2.2rem;
    font-weight: 800;
    background: var(--gradient-success);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    min-width: 120px;
    text-align: center;
}

/* ========================================
   Visualization Cards
   ======================================== */

.visualization-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 10px;
    margin-bottom: 12px;
}

.viz-card {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: 14px;
    border: 1px solid rgba(167, 139, 250, 0.1);
    transition: all var(--transition-normal);
}

.viz-card:hover {
    border-color: var(--primary);
    box-shadow: var(--shadow-glow);
}

.viz-card.wide {
    grid-column: 1 / -1;
}

.viz-card h3 {
    font-size: 0.95rem;
    margin-bottom: 8px;
    color: var(--accent-purple);
}

.viz-description {
    color: var(--text-secondary);
    font-size: 0.82rem;
    margin-top: 8px;
    text-align: center;
}

/* Pie Chart */
.pie-container {
    display: flex;
    justify-content: center;
    padding: 8px;
}

#pieChart {
    width: 140px;
    height: 140px;
    filter: drop-shadow(0 2px 8px rgba(0, 0, 0, 0.3));
}

/* Bar Model */
.bar-container {
    height: 44px;
    background: var(--bg-input);
    border-radius: var(--radius-sm);
    display: flex;
    overflow: hidden;
    border: 1px solid rgba(255, 255, 255, 0.08);
}

.bar-segment {
    height: 100%;
    transition: all var(--transition-normal);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 0.8rem;
    border-right: 1px solid rgba(255, 255, 255, 0.08);
}

.bar-segment:last-child { border-right: none; }
.bar-segment.filled { background: var(--gradient-primary); }
.bar-segment.empty { background: rgba(255, 255, 255, 0.03); color: var(--text-muted); }

/* Grid Model */
.grid-container {
    display: grid;
    gap: 2px;
    padding: 6px;
    background: var(--bg-input);
    border-radius: var(--radius-sm);
    max-width: 240px;
    margin: 0 auto;
}

.grid-cell {
    aspect-ratio: 1;
    border-radius: 3px;
    transition: all var(--transition-fast);
}

.grid-cell.filled { background: var(--gradient-primary); }
.grid-cell.empty { background: rgba(255, 255, 255, 0.07); }

/* Number Line */
.numberline-container {
    padding: 8px 4px;
}

#numberLine {
    width: 100%;
    height: 70px;
}

/* ========================================
   Fun Fact & Insight Cards
   ======================================== */

.fun-fact-card,
.insight-card {
    background: linear-gradient(135deg, rgba(167, 139, 250, 0.12) 0%, rgba(244, 114, 182, 0.1) 100%);
    border: 1px solid rgba(167, 139, 250, 0.2);
    border-radius: var(--radius-md);
    padding: 12px 16px;
    display: flex;
    align-items: center;
    gap: 10px;
}

.fun-fact-icon,
.insight-icon {
    font-size: 1.4rem;
    flex-shrink: 0;
}

.fun-fact-card p,
.insight-card p {
    font-size: 0.9rem;
    line-height: 1.4;
}

/* ========================================
   Compare Section
   ======================================== */

.compare-container {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 16px;
    margin-bottom: 16px;
    flex-wrap: wrap;
}

.compare-side {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: 14px;
    text-align: center;
    flex: 1;
    max-width: 260px;
    border: 2px solid transparent;
    transition: all var(--transition-normal);
}

.compare-side.left { border-color: var(--primary); }
.compare-side.right { border-color: var(--accent-pink); }

.compare-label {
    font-size: 0.8rem;
    color: var(--text-secondary);
    margin-bottom: 8px;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.compare-decimal {
    font-size: 1.4rem;
    font-weight: 700;
    margin: 8px 0;
    color: var(--accent-green);
}

.compare-bar-container {
    height: 22px;
    background: var(--bg-input);
    border-radius: var(--radius-sm);
    overflow: hidden;
    margin-top: 8px;
}

.compare-bar {
    height: 100%;
    transition: width var(--transition-slow);
    border-radius: var(--radius-sm);
}

.compare-side.left .compare-bar { background: var(--gradient-primary); }
.compare-side.right .compare-bar { background: var(--gradient-fun); }

.compare-result {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 2px;
}

.compare-symbol {
    font-size: 2.2rem;
    font-weight: 800;
    color: var(--secondary);
}

.compare-text {
    font-size: 0.75rem;
    color: var(--text-secondary);
}

/* Thousand Grid Compare */
.compare-visual-section {
    margin-bottom: 12px;
}

.compare-visual-section h3 {
    text-align: center;
    margin-bottom: 10px;
    font-size: 1rem;
    color: var(--accent-cyan);
}

.thousand-grid-compare {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 16px;
    flex-wrap: wrap;
}

.thousand-grid-side { text-align: center; }

.thousand-grid {
    display: grid;
    grid-template-columns: repeat(25, 1fr);
    gap: 1px;
    background: var(--bg-card);
    padding: 6px;
    border-radius: var(--radius-sm);
    max-width: 250px;
}

.thousand-cell {
    aspect-ratio: 1;
    background: rgba(255, 255, 255, 0.07);
    border-radius: 1px;
    transition: background var(--transition-fast);
}

.thousand-cell.filled { background: var(--primary); }

.grid-label {
    margin-top: 6px;
    color: var(--text-secondary);
    font-size: 0.8rem;
}

.vs-badge {
    background: var(--gradient-warning);
    color: white;
    font-weight: 800;
    padding: 8px 16px;
    border-radius: var(--radius-full);
    font-size: 0.9rem;
}

/* ========================================
   Place Value Section
   ======================================== */

.place-value-input {
    text-align: center;
    margin-bottom: 14px;
}

.place-value-input label {
    display: block;
    margin-bottom: 6px;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.big-input {
    background: var(--bg-card);
    border: 2px solid var(--primary);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-size: 2rem;
    font-weight: 700;
    padding: 10px 20px;
    text-align: center;
    font-family: inherit;
    width: 200px;
    transition: all var(--transition-fast);
}

.big-input:focus {
    outline: none;
    border-color: var(--secondary);
    box-shadow: var(--shadow-glow);
}

/* Place Value Table */
.place-value-table-container {
    overflow-x: auto;
    margin-bottom: 14px;
}

.place-value-table {
    display: flex;
    justify-content: center;
    gap: 4px;
    min-width: fit-content;
    padding: 10px;
}

.place-column {
    display: flex;
    flex-direction: column;
    align-items: center;
    min-width: 60px;
}

.place-header {
    font-size: 0.7rem;
    color: var(--text-secondary);
    margin-bottom: 6px;
    text-align: center;
    height: 34px;
    display: flex;
    align-items: center;
}

.place-digit {
    width: 50px;
    height: 56px;
    background: var(--bg-card);
    border: 2px solid var(--primary);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.6rem;
    font-weight: 800;
}

.place-digit.decimal-point {
    background: transparent;
    border: none;
    font-size: 2.2rem;
    width: 24px;
    color: var(--secondary);
}

.place-digit.highlighted {
    border-color: var(--secondary);
    background: rgba(251, 146, 60, 0.15);
}

.place-value-label {
    margin-top: 6px;
    font-size: 0.72rem;
    color: var(--accent-green);
    font-weight: 600;
}

/* Place Value two-col layout */
.pv-two-col {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 10px;
    margin-bottom: 12px;
}

/* Money Visual */
.money-visual {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: 14px;
    text-align: center;
}

.money-visual h3 {
    margin-bottom: 10px;
    font-size: 0.95rem;
    color: var(--accent-cyan);
}

.money-display {
    display: flex;
    justify-content: center;
    gap: 12px;
    flex-wrap: wrap;
    margin-bottom: 8px;
}

.money-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 4px;
}

.money-icon { font-size: 1.8rem; }

.money-count {
    background: var(--gradient-success);
    color: white;
    padding: 2px 10px;
    border-radius: var(--radius-full);
    font-weight: 700;
    font-size: 0.8rem;
}

.money-explanation {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

/* Blocks Visual */
.blocks-visual {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: 14px;
}

.blocks-visual h3 {
    text-align: center;
    margin-bottom: 4px;
    font-size: 0.95rem;
    color: var(--accent-cyan);
}

.blocks-subtitle {
    text-align: center;
    color: var(--text-secondary);
    margin-bottom: 10px;
    font-size: 0.8rem;
}

.blocks-container {
    display: flex;
    justify-content: center;
    gap: 16px;
    flex-wrap: wrap;
}

.block-group { text-align: center; }

.block-label {
    font-size: 0.75rem;
    color: var(--text-secondary);
    margin-bottom: 6px;
}

.blocks {
    display: flex;
    gap: 3px;
    flex-wrap: wrap;
    justify-content: center;
    max-width: 120px;
}

.block { border-radius: 2px; }
.block.hundred { width: 30px; height: 30px; background: var(--gradient-primary); }
.block.ten { width: 30px; height: 6px; background: var(--gradient-success); }
.block.one { width: 6px; height: 6px; background: var(--gradient-fun); }

.block-count {
    margin-top: 6px;
    font-weight: 700;
    color: var(--text-primary);
    font-size: 0.9rem;
}

/* Tips Grid */
.place-value-tips {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 10px;
}

.tip-card {
    background: var(--bg-card);
    border-radius: var(--radius-md);
    padding: 12px;
    text-align: center;
    border: 1px solid rgba(167, 139, 250, 0.1);
}

.tip-card h4 {
    margin-bottom: 4px;
    color: var(--accent-purple);
    font-size: 0.9rem;
}

.tip-card p {
    color: var(--text-secondary);
    font-size: 0.82rem;
}

/* ========================================
   Playground Section
   ======================================== */

.playground-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 10px;
}

.playground-card {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: 14px;
    border: 1px solid rgba(167, 139, 250, 0.1);
}

.playground-card.wide {
    grid-column: 1 / -1;
}

.playground-card h3 {
    font-size: 1rem;
    margin-bottom: 2px;
    color: var(--accent-purple);
}

.playground-card > p {
    color: var(--text-secondary);
    margin-bottom: 10px;
    font-size: 0.85rem;
}

/* Pizza */
.pizza-container {
    display: flex;
    justify-content: center;
    margin-bottom: 8px;
}

#pizzaSvg {
    width: 160px;
    height: 160px;
    cursor: pointer;
}

.pizza-slice {
    transition: all var(--transition-fast);
    cursor: pointer;
}

.pizza-slice:hover { filter: brightness(1.2); }
.pizza-slice.eaten { opacity: 0.15; }

.pizza-info {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 8px;
    font-size: 1.2rem;
    font-weight: 700;
    margin-bottom: 8px;
}

#pizzaFraction { color: var(--primary-light); }
#pizzaDecimal { color: var(--accent-green); }
#pizzaPercent { color: var(--text-secondary); font-size: 0.85rem; }

.reset-btn {
    display: block;
    width: 100%;
    background: var(--bg-input);
    border: 1.5px solid var(--primary);
    color: var(--text-primary);
    padding: 8px;
    border-radius: var(--radius-md);
    font-family: inherit;
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
}

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

/* Slider */
.slider-container { margin-bottom: 12px; }

.big-slider {
    width: 100%;
    height: 14px;
    -webkit-appearance: none;
    appearance: none;
    background: var(--bg-input);
    border-radius: var(--radius-full);
    outline: none;
}

.big-slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 32px;
    height: 32px;
    border-radius: 50%;
    background: var(--gradient-primary);
    cursor: pointer;
    box-shadow: var(--shadow-md);
    transition: transform var(--transition-fast);
}

.big-slider::-webkit-slider-thumb:hover { transform: scale(1.15); }

.slider-labels {
    display: flex;
    justify-content: space-between;
    margin-top: 4px;
    color: var(--text-secondary);
    font-size: 0.8rem;
}

.slider-display {
    text-align: center;
    margin-bottom: 8px;
}

.slider-value {
    font-size: 1.8rem;
    font-weight: 800;
    background: var(--gradient-success);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.slider-fraction {
    color: var(--text-secondary);
    font-size: 0.85rem;
}

.slider-bar-visual {
    height: 20px;
    background: var(--bg-input);
    border-radius: var(--radius-sm);
    overflow: hidden;
}

.slider-bar-fill {
    height: 100%;
    background: var(--gradient-primary);
    transition: width var(--transition-fast);
    border-radius: var(--radius-sm);
}

/* Match Game */
.match-game { text-align: center; }

.match-question {
    font-size: 2.2rem;
    font-weight: 800;
    color: var(--primary-light);
    margin-bottom: 12px;
}

.match-options {
    display: flex;
    justify-content: center;
    gap: 10px;
    flex-wrap: wrap;
}

.match-option {
    background: var(--bg-input);
    border: 2px solid transparent;
    color: var(--text-primary);
    padding: 10px 20px;
    border-radius: var(--radius-md);
    font-size: 1.1rem;
    font-weight: 700;
    cursor: pointer;
    transition: all var(--transition-fast);
    font-family: inherit;
}

.match-option:hover {
    border-color: var(--primary);
    transform: translateY(-2px);
}

.match-option.correct { background: var(--gradient-success); border-color: transparent; }
.match-option.wrong { background: var(--gradient-warning); border-color: transparent; }

.match-feedback {
    margin-top: 10px;
    font-size: 1rem;
    font-weight: 700;
    min-height: 28px;
}

.match-score {
    margin-top: 8px;
    font-size: 0.9rem;
    color: var(--text-secondary);
}

#matchScore { color: var(--accent-green); font-weight: 700; }

/* ========================================
   Quiz Section
   ======================================== */

.quiz-container {
    max-width: 600px;
    margin: 0 auto;
}

.quiz-progress { margin-bottom: 14px; }

.progress-bar {
    height: 10px;
    background: var(--bg-input);
    border-radius: var(--radius-full);
    overflow: hidden;
    margin-bottom: 6px;
}

.progress-fill {
    height: 100%;
    background: var(--gradient-primary);
    transition: width var(--transition-normal);
    border-radius: var(--radius-full);
}

.progress-text {
    color: var(--text-secondary);
    font-size: 0.8rem;
}

.quiz-question-card {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: 20px;
    text-align: center;
}

.question-type {
    color: var(--accent-purple);
    font-size: 0.82rem;
    margin-bottom: 8px;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.question-text {
    font-size: 1.2rem;
    font-weight: 700;
    margin-bottom: 16px;
}

.question-visual { margin-bottom: 16px; }

.answer-options {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 10px;
}

.answer-option {
    background: var(--bg-input);
    border: 2px solid transparent;
    color: var(--text-primary);
    padding: 14px;
    border-radius: var(--radius-md);
    font-size: 1.05rem;
    font-weight: 700;
    cursor: pointer;
    transition: all var(--transition-fast);
    font-family: inherit;
}

.answer-option:hover {
    border-color: var(--primary);
    transform: scale(1.02);
}

.answer-option.correct { background: var(--gradient-success); border-color: transparent; }
.answer-option.wrong { background: rgba(239, 68, 68, 0.5); border-color: #ef4444; }

.quiz-feedback {
    margin-top: 12px;
    font-size: 1rem;
    font-weight: 700;
    min-height: 30px;
    display: flex;
    align-items: center;
    justify-content: center;
}

/* Quiz Start & Results */
.quiz-start,
.quiz-results {
    max-width: 440px;
    margin: 0 auto;
}

.start-card,
.results-card {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: 28px;
    text-align: center;
}

.start-card h3,
.results-card h3 {
    font-size: 1.3rem;
    margin-bottom: 6px;
}

.start-card p {
    color: var(--text-secondary);
    margin-bottom: 16px;
    font-size: 0.9rem;
}

.difficulty-select {
    display: flex;
    justify-content: center;
    gap: 8px;
    margin-bottom: 16px;
}

.difficulty-btn {
    background: var(--bg-input);
    border: 2px solid transparent;
    color: var(--text-secondary);
    padding: 8px 16px;
    border-radius: var(--radius-md);
    font-family: inherit;
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
}

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

.difficulty-btn.active {
    background: var(--gradient-primary);
    color: white;
}

.primary-btn {
    background: var(--gradient-primary);
    border: none;
    color: white;
    padding: 12px 32px;
    border-radius: var(--radius-full);
    font-family: inherit;
    font-size: 1rem;
    font-weight: 700;
    cursor: pointer;
    transition: all var(--transition-fast);
    box-shadow: var(--shadow-md);
}

.primary-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-glow);
}

.primary-btn.big {
    padding: 14px 40px;
    font-size: 1.1rem;
}

.results-score {
    font-size: 2.4rem;
    font-weight: 800;
    background: var(--gradient-success);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin: 10px 0;
}

#resultsMessage {
    color: var(--text-secondary);
    margin-bottom: 16px;
}

.hidden {
    display: none !important;
}

/* ========================================
   Responsive Design
   ======================================== */

@media (max-width: 768px) {
    .app-container {
        padding: 8px 10px;
    }

    .app-header {
        padding: 8px 12px;
    }

    .header-row {
        flex-direction: column;
        gap: 8px;
    }

    .nav-tabs {
        justify-content: center;
    }

    .nav-tab {
        padding: 6px 10px;
        font-size: 0.8rem;
    }

    .section-header h2 {
        font-size: 1.2rem;
    }

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

    .fraction-part {
        width: 70px;
        height: 42px;
        font-size: 1.3rem;
    }

    .fraction-line { width: 84px; }
    .equals { font-size: 1.6rem; }
    .decimal-display { font-size: 1.8rem; min-width: 100px; }

    .compare-container { flex-direction: column; gap: 10px; }
    .compare-side { max-width: 100%; width: 100%; padding: 12px; }

    .thousand-grid-compare { flex-direction: column; }
    .thousand-grid { max-width: 220px; }

    .pv-two-col { grid-template-columns: 1fr; }
    .place-value-tips { grid-template-columns: 1fr; }

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

    .answer-options { grid-template-columns: 1fr; }
}

@media (max-width: 480px) {
    .input-group { gap: 10px; }

    .fraction-part {
        width: 60px;
        height: 38px;
        font-size: 1.2rem;
    }

    .big-input {
        width: 160px;
        font-size: 1.6rem;
        padding: 8px 14px;
    }

    .place-digit {
        width: 40px;
        height: 48px;
        font-size: 1.3rem;
    }

    .place-column { min-width: 44px; }

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

    /* Touch targets */
    .nav-tab {
        padding: 10px 14px;
        min-height: 44px;
    }

    .answer-option,
    .match-option,
    .difficulty-btn {
        min-height: 48px;
    }

    .reset-btn,
    .primary-btn {
        min-height: 44px;
    }
}

/* Touch device optimizations */
@media (hover: none) and (pointer: coarse) {
    .nav-tab,
    .answer-option,
    .match-option,
    .difficulty-btn,
    .reset-btn,
    .primary-btn {
        min-height: 44px;
    }

    .big-slider::-webkit-slider-thumb {
        width: 40px;
        height: 40px;
    }
}

/* ========================================
   Animations
   ======================================== */

@keyframes pulse {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.05); }
}

@keyframes shake {
    0%, 100% { transform: translateX(0); }
    25% { transform: translateX(-4px); }
    75% { transform: translateX(4px); }
}

.pulse { animation: pulse 0.5s ease; }
.shake { animation: shake 0.4s ease; }

/* Confetti */
.confetti {
    position: fixed;
    pointer-events: none;
    z-index: 1000;
}