/* ============================================
   Miao AI - Official Website Styles
   A premium, editorial aesthetic
   ============================================ */

/* CSS Custom Properties */
:root {
    /* Colors - iOS Blue palette */
    --color-primary: #007AFF;
    --color-primary-dark: #0056CC;
    --color-primary-light: #5AC8FA;
    
    /* Neutrals */
    --color-bg: #F2F2F7;
    --color-bg-alt: #FFFFFF;
    --color-surface: #FFFFFF;
    --color-text: #1C1C1E;
    --color-text-secondary: #3C3C43;
    --color-text-muted: #8E8E93;
    --color-border: #C6C6C8;
    
    /* Accents */
    --color-accent-warm: #FF9500;
    --color-accent-cool: #34C759;
    
    /* Typography */
    --font-display: 'Playfair Display', Georgia, serif;
    --font-body: 'DM Sans', -apple-system, BlinkMacSystemFont, sans-serif;
    
    /* Spacing */
    --space-xs: 0.5rem;
    --space-sm: 1rem;
    --space-md: 1.5rem;
    --space-lg: 2.5rem;
    --space-xl: 4rem;
    --space-2xl: 6rem;
    
    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 20px;
    --radius-full: 9999px;
    
    /* Shadows */
    --shadow-sm: 0 2px 8px rgba(45, 42, 38, 0.06);
    --shadow-md: 0 4px 20px rgba(45, 42, 38, 0.1);
    --shadow-lg: 0 8px 40px rgba(45, 42, 38, 0.12);
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
    --transition-slow: 400ms ease;
}

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

html {
    scroll-behavior: smooth;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-body);
    font-size: 16px;
    line-height: 1.6;
    color: var(--color-text);
    background-color: var(--color-bg);
}

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

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

ul {
    list-style: none;
}

/* Typography */
h1, h2, h3, h4 {
    font-family: var(--font-display);
    font-weight: 600;
    line-height: 1.2;
    color: var(--color-text);
}

h1 {
    font-size: clamp(2.5rem, 5vw, 4rem);
}

h2 {
    font-size: clamp(2rem, 4vw, 3rem);
}

h3 {
    font-size: clamp(1.25rem, 2vw, 1.5rem);
}

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

/* ============================================
   Navigation
   ============================================ */
.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: rgba(242, 242, 247, 0.85);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--color-border);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--space-md);
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 72px;
}

.nav-logo {
    display: flex;
    align-items: center;
    gap: var(--space-xs);
    font-family: var(--font-display);
    font-size: 1.5rem;
    font-weight: 600;
}

.logo-icon {
    display: flex;
    align-items: center;
}

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

.nav-menu a {
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--color-text-secondary);
    transition: color var(--transition-fast);
}

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

.nav-cta {
    background: var(--color-primary);
    color: white !important;
    padding: 0.6rem 1.25rem;
    border-radius: var(--radius-full);
    transition: background var(--transition-fast), transform var(--transition-fast);
}

.nav-cta:hover {
    background: var(--color-primary-dark);
    transform: translateY(-1px);
}

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
}

.nav-toggle span {
    display: block;
    width: 24px;
    height: 2px;
    background: var(--color-text);
    border-radius: 2px;
    transition: var(--transition-fast);
}

/* ============================================
   Buttons
   ============================================ */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-xs);
    font-family: var(--font-body);
    font-size: 1rem;
    font-weight: 600;
    padding: 1rem 2rem;
    border: none;
    border-radius: var(--radius-full);
    cursor: pointer;
    transition: all var(--transition-fast);
}

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

.btn-primary:hover {
    background: #1a1816;
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.btn-large {
    padding: 1.25rem 2.5rem;
    font-size: 1.1rem;
}

.apple-icon {
    width: 20px;
    height: 20px;
}

/* ============================================
   Hero Section
   ============================================ */
.hero {
    position: relative;
    min-height: 100vh;
    padding: calc(72px + var(--space-xl)) 0 var(--space-xl);
    overflow: hidden;
}

.hero-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--space-md);
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-xl);
    align-items: center;
    min-height: calc(100vh - 72px - var(--space-xl) * 2);
}

.hero-content {
    max-width: 560px;
}

.hero-title {
    margin-bottom: var(--space-md);
}

.hero-title .highlight {
    display: block;
    color: var(--color-primary);
}

.hero-subtitle {
    font-size: 1.2rem;
    color: var(--color-text-secondary);
    margin-bottom: var(--space-lg);
    line-height: 1.7;
}

.hero-cta {
    margin-bottom: var(--space-xl);
}

.hero-stats {
    display: flex;
    gap: var(--space-xl);
}

.stat {
    display: flex;
    flex-direction: column;
}

.stat-number {
    font-family: var(--font-display);
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--color-primary);
}

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

/* Phone Mockup */
.hero-visual {
    display: flex;
    justify-content: center;
    align-items: center;
}

.phone-mockup {
    width: 280px;
    height: 560px;
    background: var(--color-text);
    border-radius: 40px;
    padding: 12px;
    box-shadow: var(--shadow-lg), 0 0 0 1px rgba(0,0,0,0.1);
    transform: rotate(3deg);
    animation: float 6s ease-in-out infinite;
}

@keyframes float {
    0%, 100% { transform: rotate(3deg) translateY(0); }
    50% { transform: rotate(3deg) translateY(-15px); }
}

.phone-screen {
    width: 100%;
    height: 100%;
    background: var(--color-surface);
    border-radius: 30px;
    overflow: hidden;
}

.screen-content {
    padding: var(--space-md);
    height: 100%;
    display: flex;
    flex-direction: column;
}

.mock-header {
    text-align: center;
    padding-bottom: var(--space-sm);
    border-bottom: 1px solid var(--color-border);
    margin-bottom: var(--space-md);
}

.mock-title {
    font-family: var(--font-display);
    font-weight: 600;
    font-size: 1.1rem;
}

.mock-story {
    flex: 1;
}

.mock-story h3 {
    font-size: 1.2rem;
    margin-bottom: var(--space-sm);
}

.mock-story p {
    font-size: 0.9rem;
    color: var(--color-text-secondary);
    line-height: 1.6;
    margin-bottom: var(--space-md);
}

.mock-word {
    display: inline-flex;
    flex-direction: column;
    background: var(--color-bg-alt);
    padding: var(--space-xs) var(--space-sm);
    border-radius: var(--radius-sm);
    border-left: 3px solid var(--color-primary);
}

.mock-word .word {
    font-weight: 600;
    color: var(--color-primary);
}

.mock-word .translation {
    font-size: 0.8rem;
    color: var(--color-text-muted);
}

.mock-progress {
    margin-top: auto;
    padding-top: var(--space-md);
    border-top: 1px solid var(--color-border);
}

.progress-bar {
    height: 6px;
    background: var(--color-border);
    border-radius: var(--radius-full);
    margin-bottom: var(--space-xs);
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    width: 40%;
    background: linear-gradient(90deg, var(--color-primary), var(--color-primary-light));
    border-radius: var(--radius-full);
}

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

/* Hero Background */
.hero-bg-shape {
    position: absolute;
    top: -50%;
    right: -20%;
    width: 80%;
    height: 150%;
    background: linear-gradient(135deg, var(--color-bg-alt) 0%, transparent 60%);
    border-radius: 50%;
    z-index: -1;
    opacity: 0.7;
}

/* ============================================
   Section Styles
   ============================================ */
.section-header {
    text-align: center;
    max-width: 640px;
    margin: 0 auto var(--space-xl);
}

.section-title {
    margin-bottom: var(--space-sm);
}

.section-subtitle {
    font-size: 1.1rem;
    color: var(--color-text-secondary);
}

/* ============================================
   Features Section
   ============================================ */
.features {
    padding: var(--space-2xl) 0;
    background: var(--color-surface);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-lg);
}

.feature-card {
    padding: var(--space-lg);
    background: var(--color-bg);
    border-radius: var(--radius-lg);
    transition: transform var(--transition-base), box-shadow var(--transition-base);
}

.feature-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
}

.feature-icon {
    width: 56px;
    height: 56px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-light) 100%);
    border-radius: var(--radius-md);
    margin-bottom: var(--space-md);
    color: white;
}

.feature-icon svg {
    width: 28px;
    height: 28px;
}

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

.feature-card p {
    color: var(--color-text-secondary);
    font-size: 0.95rem;
}

/* ============================================
   How It Works Section
   ============================================ */
.how-it-works {
    padding: var(--space-2xl) 0;
}

.steps {
    display: flex;
    flex-direction: column;
    gap: var(--space-xl);
}

.step {
    display: grid;
    grid-template-columns: 60px 1fr 1fr;
    gap: var(--space-lg);
    align-items: center;
}

.step:nth-child(even) {
    direction: rtl;
}

.step:nth-child(even) > * {
    direction: ltr;
}

.step-number {
    width: 60px;
    height: 60px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: var(--font-display);
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--color-primary);
    background: var(--color-bg-alt);
    border-radius: 50%;
    border: 2px solid var(--color-primary);
}

.step-content h3 {
    margin-bottom: var(--space-xs);
}

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

.step-visual {
    display: flex;
    justify-content: center;
}

/* Level Cards */
.level-cards {
    display: flex;
    gap: var(--space-sm);
}

.level-card {
    width: 60px;
    height: 60px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: var(--font-display);
    font-weight: 600;
    background: var(--color-surface);
    border: 2px solid var(--color-border);
    border-radius: var(--radius-md);
    color: var(--color-text-muted);
    transition: all var(--transition-fast);
}

.level-card.active {
    background: var(--color-primary);
    border-color: var(--color-primary);
    color: white;
    transform: scale(1.1);
}

/* Story Snippet */
.story-snippet {
    background: var(--color-surface);
    padding: var(--space-md);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    max-width: 300px;
}

.story-snippet p {
    font-size: 0.95rem;
    color: var(--color-text-secondary);
}

.highlighted-word {
    background: linear-gradient(120deg, var(--color-accent-warm) 0%, var(--color-accent-warm) 100%);
    background-size: 100% 40%;
    background-position: 0 90%;
    background-repeat: no-repeat;
    font-weight: 600;
    color: var(--color-text);
}

/* Exercise Preview */
.exercise-preview {
    background: var(--color-surface);
    padding: var(--space-md);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    max-width: 280px;
}

.exercise-label {
    font-size: 0.8rem;
    color: var(--color-text-muted);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.exercise-preview p {
    font-size: 1rem;
    margin: var(--space-xs) 0 var(--space-sm);
}

.exercise-options {
    display: flex;
    gap: var(--space-xs);
}

.option {
    padding: 0.4rem 0.8rem;
    background: var(--color-bg);
    border-radius: var(--radius-full);
    font-size: 0.85rem;
    color: var(--color-text-secondary);
}

.option.correct {
    background: #34C759;
    color: white;
}

/* ============================================
   Languages Section
   ============================================ */
.languages {
    padding: var(--space-xl) 0 var(--space-2xl);
    text-align: center;
}

.languages .section-title {
    margin-bottom: var(--space-lg);
}

.language-grid {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: var(--space-md);
    max-width: 800px;
    margin: 0 auto;
}

.language-item {
    display: flex;
    align-items: center;
    gap: var(--space-xs);
    padding: 0.75rem 1.25rem;
    background: var(--color-surface);
    border-radius: var(--radius-full);
    box-shadow: var(--shadow-sm);
    transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

.language-item:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.language-flag {
    font-size: 1.5rem;
}

.language-name {
    font-weight: 500;
}

/* ============================================
   Download CTA Section
   ============================================ */
.download-cta {
    padding: var(--space-2xl) 0;
    background: linear-gradient(135deg, var(--color-text) 0%, #1a1816 100%);
    color: white;
    text-align: center;
}

.cta-content {
    max-width: 600px;
    margin: 0 auto;
}

.cta-content h2 {
    color: white;
    margin-bottom: var(--space-sm);
}

.cta-content p {
    color: rgba(255, 255, 255, 0.7);
    font-size: 1.1rem;
    margin-bottom: var(--space-lg);
}

.download-cta .btn-primary {
    background: var(--color-primary);
}

.download-cta .btn-primary:hover {
    background: var(--color-primary-light);
    color: var(--color-text);
}

/* ============================================
   Footer
   ============================================ */
.footer {
    padding: var(--space-xl) 0 var(--space-lg);
    background: var(--color-bg-alt);
    border-top: 1px solid var(--color-border);
}

.footer-content {
    display: grid;
    grid-template-columns: 1.5fr 2fr;
    gap: var(--space-xl);
    margin-bottom: var(--space-lg);
}

.footer-logo {
    display: inline-flex;
    align-items: center;
    gap: var(--space-xs);
    font-family: var(--font-display);
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: var(--space-sm);
}

.footer-brand p {
    color: var(--color-text-secondary);
    font-size: 0.95rem;
}

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

.footer-column h4 {
    font-family: var(--font-body);
    font-size: 0.85rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--color-text-muted);
    margin-bottom: var(--space-sm);
}

.footer-column ul {
    display: flex;
    flex-direction: column;
    gap: var(--space-xs);
}

.footer-column a {
    font-size: 0.95rem;
    color: var(--color-text-secondary);
    transition: color var(--transition-fast);
}

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

.footer-bottom {
    padding-top: var(--space-lg);
    border-top: 1px solid var(--color-border);
    text-align: center;
}

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

/* ============================================
   Responsive Design
   ============================================ */
@media (max-width: 1024px) {
    .hero-container {
        grid-template-columns: 1fr;
        text-align: center;
        gap: var(--space-lg);
    }
    
    .hero-content {
        max-width: 100%;
    }
    
    .hero-stats {
        justify-content: center;
    }
    
    .phone-mockup {
        width: 240px;
        height: 480px;
        transform: rotate(0);
    }
    
    @keyframes float {
        0%, 100% { transform: translateY(0); }
        50% { transform: translateY(-10px); }
    }
    
    .step {
        grid-template-columns: 1fr;
        text-align: center;
    }
    
    .step:nth-child(even) {
        direction: ltr;
    }
    
    .step-number {
        margin: 0 auto;
    }
    
    .features-grid {
        grid-template-columns: 1fr;
    }
    
    .footer-content {
        grid-template-columns: 1fr;
        text-align: center;
    }
    
    .footer-links {
        justify-items: center;
    }
}

@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        top: 72px;
        left: 0;
        right: 0;
        background: var(--color-surface);
        flex-direction: column;
        padding: var(--space-md);
        gap: var(--space-sm);
        border-bottom: 1px solid var(--color-border);
        transform: translateY(-100%);
        opacity: 0;
        visibility: hidden;
        transition: all var(--transition-base);
    }
    
    .nav-menu.active {
        transform: translateY(0);
        opacity: 1;
        visibility: visible;
    }
    
    .nav-toggle {
        display: flex;
    }
    
    .nav-toggle.active span:nth-child(1) {
        transform: rotate(45deg) translate(5px, 5px);
    }
    
    .nav-toggle.active span:nth-child(2) {
        opacity: 0;
    }
    
    .nav-toggle.active span:nth-child(3) {
        transform: rotate(-45deg) translate(5px, -5px);
    }
    
    .hero {
        padding-top: calc(72px + var(--space-lg));
    }
    
    .hero-stats {
        flex-direction: column;
        gap: var(--space-sm);
    }
    
    .stat {
        flex-direction: row;
        gap: var(--space-xs);
        align-items: center;
    }
    
    .footer-links {
        grid-template-columns: 1fr;
        gap: var(--space-md);
    }
}

@media (max-width: 480px) {
    :root {
        --space-lg: 2rem;
        --space-xl: 3rem;
        --space-2xl: 4rem;
    }
    
    .btn {
        width: 100%;
    }
    
    .phone-mockup {
        width: 220px;
        height: 440px;
    }
    
    .language-grid {
        gap: var(--space-xs);
    }
    
    .language-item {
        padding: 0.5rem 1rem;
        font-size: 0.9rem;
    }
}

/* ============================================
   Animations
   ============================================ */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.hero-content {
    animation: fadeInUp 0.8s ease-out;
}

.hero-visual {
    animation: fadeInUp 0.8s ease-out 0.2s both;
}

.feature-card {
    opacity: 0;
    animation: fadeInUp 0.6s ease-out forwards;
}

.feature-card:nth-child(1) { animation-delay: 0.1s; }
.feature-card:nth-child(2) { animation-delay: 0.2s; }
.feature-card:nth-child(3) { animation-delay: 0.3s; }
.feature-card:nth-child(4) { animation-delay: 0.4s; }

/* Scroll-triggered animations */
@media (prefers-reduced-motion: no-preference) {
    .step {
        opacity: 0;
        transform: translateY(30px);
        transition: opacity 0.6s ease, transform 0.6s ease;
    }
    
    .step.visible {
        opacity: 1;
        transform: translateY(0);
    }
}