/* YoTu Landing Page Styles */
/* Purple/Violet Theme */

:root {
    /* Colors */
    --primary: #8B5CF6;
    --primary-dark: #7C3AED;
    --primary-light: #A78BFA;
    --primary-glow: rgba(139, 92, 246, 0.3);

    --bg-dark: #0F0F1A;
    --bg-surface: #1A1A2E;
    --bg-card: #16162A;
    --bg-elevated: #252540;

    --text-primary: #FFFFFF;
    --text-secondary: #A0A0B8;
    --text-muted: #6B6B80;

    --accent: #C4B5FD;
    --success: #10B981;
    --warning: #F59E0B;

    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-2xl: 4rem;
    --spacing-3xl: 6rem;

    /* Border Radius */
    --radius-sm: 0.5rem;
    --radius-md: 0.75rem;
    --radius-lg: 1rem;
    --radius-xl: 1.5rem;

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 250ms ease;
    --transition-slow: 350ms ease;

    /* Font */
    --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-sans);
    background-color: var(--bg-dark);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
}

a {
    color: inherit;
    text-decoration: none;
}

img {
    max-width: 100%;
    height: auto;
}

/* Container */
.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    line-height: 1.2;
    font-weight: 700;
}

.section-title {
    font-size: clamp(2rem, 5vw, 3.5rem);
    text-align: center;
    margin-bottom: var(--spacing-md);
}

.section-subtitle {
    font-size: 1.125rem;
    color: var(--text-secondary);
    text-align: center;
    margin-bottom: var(--spacing-xl);
}

.gradient-text {
    background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-xs);
    padding: 0.875rem 1.5rem;
    font-size: 1rem;
    font-weight: 600;
    border-radius: var(--radius-md);
    border: none;
    cursor: pointer;
    transition: all var(--transition-normal);
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    color: white;
    box-shadow: 0 4px 15px var(--primary-glow);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px var(--primary-glow);
}

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

.btn-outline:hover {
    border-color: var(--primary);
    background: rgba(139, 92, 246, 0.1);
}

.btn-small {
    padding: 0.5rem 1rem;
    font-size: 0.875rem;
}

/* Navigation */
.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: rgba(15, 15, 26, 0.8);
    backdrop-filter: blur(20px);
    border-bottom: 1px solid rgba(255, 255, 255, 0.05);
}

.nav-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-sm) var(--spacing-md);
}

.nav-logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    font-size: 1.5rem;
    font-weight: 700;
}

.logo-icon {
    width: 36px;
    height: 36px;
}

.nav-links {
    display: flex;
    align-items: center;
    gap: var(--spacing-lg);
}

.nav-links a {
    color: var(--text-secondary);
    transition: color var(--transition-fast);
}

.nav-links a:hover {
    color: var(--text-primary);
}

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 5px;
}

.nav-toggle span {
    width: 24px;
    height: 2px;
    background: var(--text-primary);
    transition: all var(--transition-fast);
}

/* Mobile Menu */
.mobile-menu {
    display: none;
    position: fixed;
    top: 65px;
    left: 0;
    right: 0;
    background: var(--bg-surface);
    padding: var(--spacing-lg);
    flex-direction: column;
    gap: var(--spacing-md);
    z-index: 999;
    border-bottom: 1px solid rgba(255, 255, 255, 0.05);
}

.mobile-menu.active {
    display: flex;
}

.mobile-menu a {
    color: var(--text-secondary);
    font-size: 1.125rem;
}

/* Hero Section */
.hero {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    padding: calc(80px + var(--spacing-xl)) 0 var(--spacing-xl);
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(ellipse at center, var(--primary-glow) 0%, transparent 50%);
    opacity: 0.3;
    animation: pulse 8s ease-in-out infinite;
}

@keyframes pulse {
    0%, 100% { transform: scale(1); opacity: 0.3; }
    50% { transform: scale(1.1); opacity: 0.4; }
}

.hero .container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-2xl);
    align-items: center;
    position: relative;
    z-index: 1;
}

.hero-content {
    max-width: 600px;
}

.hero-title {
    font-size: clamp(2.5rem, 6vw, 4rem);
    margin-bottom: var(--spacing-md);
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-lg);
}

.hero-cta {
    margin-bottom: var(--spacing-lg);
}

.app-store-badge img {
    height: 54px;
    transition: transform var(--transition-normal);
}

.app-store-badge:hover img {
    transform: scale(1.05);
}

.app-store-badge.large img {
    height: 64px;
}

.trust-badges {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-md);
}

.trust-badge {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.trust-badge .stars {
    color: var(--warning);
}

.trust-badge .icon {
    font-size: 1rem;
}

/* Hero Visual */
.hero-visual {
    display: flex;
    justify-content: center;
}

.phone-mockup {
    width: 280px;
    height: 560px;
    background: linear-gradient(180deg, #2A2A4A 0%, #1A1A2E 100%);
    border-radius: 40px;
    padding: 12px;
    box-shadow:
        0 0 0 4px #1A1A2E,
        0 20px 50px rgba(0, 0, 0, 0.5),
        0 0 100px var(--primary-glow);
}

.phone-screen {
    width: 100%;
    height: 100%;
    background: var(--bg-dark);
    border-radius: 32px;
    overflow: hidden;
}

.app-preview {
    padding: var(--spacing-md);
}

.preview-header {
    margin-bottom: var(--spacing-md);
}

.preview-title {
    font-weight: 600;
    font-size: 1.125rem;
}

.preview-card {
    display: flex;
    gap: var(--spacing-sm);
    background: var(--bg-surface);
    padding: var(--spacing-sm);
    border-radius: var(--radius-md);
    margin-bottom: var(--spacing-sm);
}

.preview-thumbnail {
    width: 60px;
    height: 45px;
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    border-radius: var(--radius-sm);
    flex-shrink: 0;
}

.preview-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.preview-line {
    height: 8px;
    background: var(--bg-elevated);
    border-radius: 4px;
}

.preview-line.long { width: 100%; }
.preview-line.medium { width: 75%; }
.preview-line.short { width: 50%; }

/* Scroll Indicator */
.scroll-indicator {
    position: absolute;
    bottom: var(--spacing-lg);
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-xs);
    color: var(--text-muted);
    font-size: 0.875rem;
    animation: bounce 2s infinite;
}

@keyframes bounce {
    0%, 100% { transform: translateX(-50%) translateY(0); }
    50% { transform: translateX(-50%) translateY(10px); }
}

/* Problem Section */
.problem-section {
    padding: var(--spacing-3xl) 0;
    background: var(--bg-surface);
}

.problem-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--spacing-lg);
}

.problem-card {
    background: var(--bg-card);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    border: 1px solid rgba(255, 255, 255, 0.05);
}

.problem-card.solution {
    border-color: var(--primary);
    background: linear-gradient(180deg, rgba(139, 92, 246, 0.1) 0%, var(--bg-card) 100%);
}

.problem-icon {
    font-size: 2.5rem;
    margin-bottom: var(--spacing-sm);
}

.problem-card h3 {
    margin-bottom: var(--spacing-sm);
    color: var(--text-secondary);
    font-size: 0.875rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.problem-card ul {
    list-style: none;
}

.problem-card li {
    padding: var(--spacing-xs) 0;
    color: var(--text-secondary);
}

.problem-card.solution li {
    color: var(--text-primary);
}

/* How It Works */
.how-it-works {
    padding: var(--spacing-3xl) 0;
}

.steps-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
}

.step {
    text-align: center;
    position: relative;
}

.step-number {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    border-radius: 50%;
    font-weight: 700;
    margin-bottom: var(--spacing-md);
}

.step-icon {
    width: 64px;
    height: 64px;
    margin: 0 auto var(--spacing-md);
    color: var(--primary-light);
}

.step h3 {
    margin-bottom: var(--spacing-sm);
}

.step p {
    color: var(--text-secondary);
}

.cta-center {
    text-align: center;
}

/* Features Section */
.features-section {
    padding: var(--spacing-3xl) 0;
    background: var(--bg-surface);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--spacing-lg);
}

.feature-card {
    background: var(--bg-card);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    border: 1px solid rgba(255, 255, 255, 0.05);
    transition: all var(--transition-normal);
}

.feature-card:hover {
    transform: translateY(-4px);
    border-color: var(--primary);
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
}

.feature-icon {
    font-size: 2.5rem;
    margin-bottom: var(--spacing-sm);
}

.feature-card h3 {
    margin-bottom: var(--spacing-xs);
}

.feature-card p {
    color: var(--text-secondary);
    font-size: 0.9375rem;
}

/* Social Proof */
.social-proof {
    padding: var(--spacing-3xl) 0;
}

.testimonials-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
}

.testimonial-card {
    background: var(--bg-surface);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    border: 1px solid rgba(255, 255, 255, 0.05);
}

.testimonial-stars {
    color: var(--warning);
    font-size: 1.25rem;
    margin-bottom: var(--spacing-sm);
}

.testimonial-text {
    font-size: 1.0625rem;
    margin-bottom: var(--spacing-md);
    font-style: italic;
}

.testimonial-author {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.author-avatar {
    width: 44px;
    height: 44px;
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 0.875rem;
}

.author-info {
    display: flex;
    flex-direction: column;
}

.author-name {
    font-weight: 600;
}

.author-role {
    font-size: 0.875rem;
    color: var(--text-muted);
}

/* Stats Bar */
.stats-bar {
    display: flex;
    justify-content: center;
    gap: var(--spacing-2xl);
    padding: var(--spacing-lg);
    background: var(--bg-surface);
    border-radius: var(--radius-lg);
}

.stat {
    text-align: center;
}

.stat-number {
    display: block;
    font-size: 2rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.stat-label {
    font-size: 0.875rem;
    color: var(--text-muted);
}

/* Pricing Section */
.pricing-section {
    padding: var(--spacing-3xl) 0;
    background: var(--bg-surface);
}

.pricing-toggle {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-xl);
}

.toggle-label {
    color: var(--text-muted);
    cursor: pointer;
    transition: color var(--transition-fast);
}

.toggle-label.active {
    color: var(--text-primary);
}

.save-badge {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    padding: 2px 8px;
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
    font-weight: 600;
}

.toggle-switch {
    width: 50px;
    height: 26px;
    background: var(--bg-elevated);
    border: none;
    border-radius: 13px;
    cursor: pointer;
    position: relative;
    transition: background var(--transition-fast);
}

.toggle-slider {
    position: absolute;
    top: 3px;
    left: 3px;
    width: 20px;
    height: 20px;
    background: var(--primary);
    border-radius: 50%;
    transition: transform var(--transition-fast);
}

.toggle-switch[data-active="yearly"] .toggle-slider {
    transform: translateX(24px);
}

.pricing-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
}

.pricing-card {
    background: var(--bg-card);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    border: 1px solid rgba(255, 255, 255, 0.05);
    position: relative;
}

.pricing-card.popular {
    border-color: var(--primary);
    background: linear-gradient(180deg, rgba(139, 92, 246, 0.15) 0%, var(--bg-card) 100%);
    transform: scale(1.05);
}

.popular-badge {
    position: absolute;
    top: -12px;
    left: 50%;
    transform: translateX(-50%);
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    padding: 4px 16px;
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
    font-weight: 600;
}

.pricing-header {
    text-align: center;
    margin-bottom: var(--spacing-md);
    padding-bottom: var(--spacing-md);
    border-bottom: 1px solid rgba(255, 255, 255, 0.05);
}

.pricing-header h3 {
    margin-bottom: var(--spacing-sm);
}

.price {
    display: flex;
    align-items: baseline;
    justify-content: center;
    gap: 4px;
}

.price-amount {
    font-size: 2.5rem;
    font-weight: 700;
}

.price-period {
    color: var(--text-muted);
}

.pricing-features {
    list-style: none;
    margin-bottom: var(--spacing-lg);
}

.pricing-features li {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-xs) 0;
    color: var(--text-secondary);
}

.pricing-features .check {
    color: var(--success);
    font-weight: 700;
}

.pricing-card .btn {
    width: 100%;
}

.pricing-note {
    text-align: center;
    color: var(--text-muted);
    font-size: 0.875rem;
}

/* FAQ Section */
.faq-section {
    padding: var(--spacing-3xl) 0;
}

.faq-grid {
    max-width: 800px;
    margin: 0 auto;
}

.faq-item {
    border-bottom: 1px solid rgba(255, 255, 255, 0.05);
}

.faq-question {
    width: 100%;
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-md) 0;
    background: none;
    border: none;
    color: var(--text-primary);
    font-size: 1.0625rem;
    font-weight: 600;
    text-align: left;
    cursor: pointer;
}

.faq-icon {
    width: 24px;
    height: 24px;
    flex-shrink: 0;
    color: var(--text-muted);
    transition: transform var(--transition-normal);
}

.faq-item.active .faq-icon {
    transform: rotate(180deg);
}

.faq-answer {
    max-height: 0;
    overflow: hidden;
    transition: max-height var(--transition-normal);
}

.faq-item.active .faq-answer {
    max-height: 200px;
}

.faq-answer p {
    padding-bottom: var(--spacing-md);
    color: var(--text-secondary);
}

.faq-answer a {
    color: var(--primary-light);
}

/* Final CTA */
.final-cta {
    padding: var(--spacing-3xl) 0;
    background: linear-gradient(180deg, var(--bg-surface) 0%, var(--bg-dark) 100%);
    text-align: center;
    position: relative;
    overflow: hidden;
}

.final-cta::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 800px;
    height: 800px;
    background: radial-gradient(ellipse at center, var(--primary-glow) 0%, transparent 50%);
    opacity: 0.3;
}

.final-cta .container {
    position: relative;
    z-index: 1;
}

.final-cta .section-title {
    margin-bottom: var(--spacing-sm);
}

.cta-note {
    margin-top: var(--spacing-md);
    color: var(--text-muted);
    font-size: 0.875rem;
}

/* Footer */
.footer {
    padding: var(--spacing-2xl) 0 var(--spacing-lg);
    background: var(--bg-dark);
    border-top: 1px solid rgba(255, 255, 255, 0.05);
}

.footer-content {
    display: grid;
    grid-template-columns: 1fr 2fr;
    gap: var(--spacing-2xl);
    margin-bottom: var(--spacing-xl);
}

.footer-logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
}

.footer-brand p {
    color: var(--text-muted);
    font-size: 0.875rem;
}

.footer-links {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--spacing-lg);
}

.footer-column h4 {
    color: var(--text-secondary);
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    margin-bottom: var(--spacing-sm);
}

.footer-column a {
    display: block;
    color: var(--text-muted);
    font-size: 0.9375rem;
    padding: var(--spacing-xs) 0;
    transition: color var(--transition-fast);
}

.footer-column a:hover {
    color: var(--text-primary);
}

.footer-bottom {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding-top: var(--spacing-lg);
    border-top: 1px solid rgba(255, 255, 255, 0.05);
}

.footer-bottom p {
    color: var(--text-muted);
    font-size: 0.875rem;
}

.footer-badge img {
    height: 40px;
    opacity: 0.7;
    transition: opacity var(--transition-fast);
}

.footer-badge:hover img {
    opacity: 1;
}

/* Responsive */
@media (max-width: 1024px) {
    .hero .container {
        grid-template-columns: 1fr;
        text-align: center;
    }

    .hero-content {
        max-width: 100%;
    }

    .trust-badges {
        justify-content: center;
    }

    .hero-visual {
        display: none;
    }

    .problem-grid,
    .steps-grid,
    .features-grid,
    .testimonials-grid,
    .pricing-grid {
        grid-template-columns: 1fr;
    }

    .pricing-card.popular {
        transform: none;
    }

    .stats-bar {
        flex-direction: column;
        gap: var(--spacing-md);
    }

    .footer-content {
        grid-template-columns: 1fr;
    }

    .footer-links {
        grid-template-columns: repeat(3, 1fr);
    }
}

@media (max-width: 768px) {
    .nav-links {
        display: none;
    }

    .nav-toggle {
        display: flex;
    }

    .section-title {
        font-size: clamp(1.75rem, 5vw, 2.5rem);
    }

    .steps-grid {
        gap: var(--spacing-xl);
    }

    .footer-links {
        grid-template-columns: 1fr 1fr;
        gap: var(--spacing-md);
    }

    .footer-bottom {
        flex-direction: column;
        gap: var(--spacing-md);
        text-align: center;
    }
}

@media (max-width: 480px) {
    .trust-badges {
        flex-direction: column;
        align-items: center;
    }

    .footer-links {
        grid-template-columns: 1fr;
    }
}

/* Animations */
.fade-in {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
    opacity: 1;
    transform: translateY(0);
}