/* ================================
   CSS Reset & Base Styles
   ================================ */

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    /* Colors */
    --primary-color: #007AFF;
    --primary-dark: #0051D5;
    --secondary-color: #5856D6;
    --text-dark: #1D1D1F;
    --text-light: #6E6E73;
    --background: #FFFFFF;
    --background-light: #F5F5F7;
    --border-color: #D2D2D7;
    --success-color: #34C759;
    --gradient-1: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --gradient-2: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    --gradient-3: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);

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

    /* Typography */
    --font-primary: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    --font-size-xs: 0.875rem;
    --font-size-sm: 1rem;
    --font-size-md: 1.125rem;
    --font-size-lg: 1.5rem;
    --font-size-xl: 2rem;
    --font-size-xxl: 3rem;

    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;

    /* Shadows */
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.08);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.12);

    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 16px;
    --radius-lg: 24px;
}

html {
    scroll-behavior: smooth;
}

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

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

a {
    text-decoration: none;
    color: inherit;
    transition: var(--transition-normal);
}

ul {
    list-style: none;
}

/* ================================
   Container & Layout
   ================================ */

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

section {
    padding: var(--spacing-xl) 0;
}

/* ================================
   Typography
   ================================ */

.section-title {
    font-size: clamp(1.75rem, 4vw, 2.5rem);
    font-weight: 700;
    text-align: center;
    margin-bottom: var(--spacing-lg);
    color: var(--text-dark);
    line-height: 1.2;
}

/* ================================
   Buttons
   ================================ */

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-xs);
    padding: 1rem 2rem;
    font-size: var(--font-size-md);
    font-weight: 600;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all var(--transition-normal);
    border: none;
    white-space: nowrap;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
    box-shadow: var(--shadow-md);
}

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

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

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

.btn-download {
    background: var(--text-dark);
    color: white;
    padding: 1.25rem 2.5rem;
    font-size: var(--font-size-lg);
    box-shadow: var(--shadow-lg);
}

.btn-download:hover {
    background: #000;
    transform: translateY(-3px);
    box-shadow: 0 12px 40px rgba(0, 0, 0, 0.2);
}

/* ================================
   Hero Section
   ================================ */

.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    position: relative;
    overflow: hidden;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    padding: var(--spacing-lg) 0;
}

.hero-background {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    opacity: 0.1;
    background-image: radial-gradient(circle at 20% 50%, white 2px, transparent 2px),
                      radial-gradient(circle at 80% 80%, white 2px, transparent 2px);
    background-size: 100px 100px;
    animation: float 20s ease-in-out infinite;
}

@keyframes float {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-20px); }
}

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

.hero-content {
    color: white;
}

.hero-icon {
    width: 100px;
    height: 100px;
    margin-bottom: var(--spacing-md);
    animation: bounce 2s infinite;
}

.hero-icon img {
    width: 100%;
    height: 100%;
    object-fit: contain;
}

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

.hero-title {
    font-size: clamp(2.5rem, 6vw, 4rem);
    font-weight: 800;
    margin-bottom: var(--spacing-sm);
    line-height: 1.1;
}

.hero-subtitle {
    font-size: clamp(1.25rem, 3vw, 1.75rem);
    font-weight: 600;
    margin-bottom: var(--spacing-md);
    opacity: 0.95;
}

.hero-description {
    font-size: var(--font-size-md);
    margin-bottom: var(--spacing-lg);
    opacity: 0.9;
    line-height: 1.8;
}

.hero-cta {
    display: flex;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
}

.hero-image {
    max-width: 500px;
    margin: 0 auto;
}

.hero-image img {
    transition: transform var(--transition-slow);
}

.hero-image img:hover {
    transform: scale(1.05);
}

.scroll-indicator {
    position: absolute;
    bottom: 40px;
    left: 50%;
    transform: translateX(-50%);
    z-index: 2;
}

.scroll-indicator span {
    display: block;
    width: 30px;
    height: 50px;
    border: 2px solid rgba(255, 255, 255, 0.5);
    border-radius: 25px;
    position: relative;
}

.scroll-indicator span::before {
    content: '';
    position: absolute;
    top: 10px;
    left: 50%;
    transform: translateX(-50%);
    width: 6px;
    height: 6px;
    background: white;
    border-radius: 50%;
    animation: scroll 2s infinite;
}

@keyframes scroll {
    0% { top: 10px; opacity: 1; }
    100% { top: 30px; opacity: 0; }
}

/* ================================
   Problem Section
   ================================ */

.problem-section {
    background: var(--background-light);
}

.problem-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-md);
    margin-top: var(--spacing-lg);
}

.problem-card {
    background: white;
    padding: var(--spacing-lg);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    transition: all var(--transition-normal);
    text-align: center;
}

.problem-card:hover {
    transform: translateY(-10px);
    box-shadow: var(--shadow-lg);
}

.problem-icon {
    font-size: 4rem;
    margin-bottom: var(--spacing-sm);
}

.problem-card h3 {
    font-size: var(--font-size-lg);
    margin-bottom: var(--spacing-sm);
    color: var(--text-dark);
}

.problem-card p {
    color: var(--text-light);
    line-height: 1.8;
}

/* ================================
   Features Section
   ================================ */

.features-section {
    background: white;
}

.features-grid {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xl);
}

.feature-item {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-lg);
    align-items: center;
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    background: var(--background-light);
    transition: all var(--transition-normal);
}

.feature-item:hover {
    box-shadow: var(--shadow-lg);
    transform: scale(1.02);
}

.feature-item-reverse {
    direction: rtl;
}

.feature-item-reverse > * {
    direction: ltr;
}

.feature-content {
    padding: var(--spacing-md);
}

.feature-icon {
    font-size: 3rem;
    margin-bottom: var(--spacing-sm);
}

.feature-item h3 {
    font-size: var(--font-size-xl);
    margin-bottom: var(--spacing-sm);
    color: var(--text-dark);
}

.feature-description {
    color: var(--text-light);
    margin-bottom: var(--spacing-md);
    line-height: 1.8;
}

.feature-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.feature-list li {
    position: relative;
    padding-left: 1.5rem;
    color: var(--text-dark);
}

.feature-list li::before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--success-color);
    font-weight: bold;
}

.feature-image {
    max-width: 400px;
    margin: 0 auto;
}

.feature-image img {
    transition: transform var(--transition-slow);
}

.feature-image img:hover {
    transform: scale(1.02);
}

/* ================================
   Highlights Section
   ================================ */

.highlights-section {
    background: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
    color: white;
}

.highlights-section .section-title {
    color: white;
}

.highlights-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-md);
}

.highlight-card {
    background: rgba(255, 255, 255, 0.15);
    backdrop-filter: blur(10px);
    padding: var(--spacing-lg);
    border-radius: var(--radius-md);
    border: 1px solid rgba(255, 255, 255, 0.2);
    transition: all var(--transition-normal);
}

.highlight-card:hover {
    background: rgba(255, 255, 255, 0.25);
    transform: translateY(-10px);
}

.highlight-number {
    font-size: 3rem;
    font-weight: 800;
    opacity: 0.3;
    margin-bottom: var(--spacing-sm);
}

.highlight-card h3 {
    font-size: var(--font-size-lg);
    margin-bottom: var(--spacing-sm);
}

.highlight-card p {
    opacity: 0.9;
    line-height: 1.8;
}

/* ================================
   Download Section
   ================================ */

.download-section {
    background: var(--text-dark);
    color: white;
    text-align: center;
}

.download-content h2 {
    font-size: clamp(2rem, 5vw, 3rem);
    margin-bottom: var(--spacing-sm);
}

.download-subtitle {
    font-size: var(--font-size-lg);
    opacity: 0.9;
    margin-bottom: var(--spacing-lg);
}

.download-buttons {
    display: flex;
    justify-content: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
}

.download-note {
    opacity: 0.7;
    font-size: var(--font-size-xs);
}

/* ================================
   FAQ Section
   ================================ */

.faq-section {
    background: var(--background-light);
}

.faq-subtitle {
    text-align: center;
    font-size: var(--font-size-md);
    color: var(--text-light);
    margin-top: -var(--spacing-md);
    margin-bottom: var(--spacing-lg);
}

.faq-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--spacing-sm);
    max-width: 900px;
    margin: 0 auto;
}

.faq-item {
    background: white;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    overflow: hidden;
    transition: all var(--transition-normal);
}

.faq-item:hover {
    box-shadow: var(--shadow-md);
}

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

.faq-question:hover {
    color: var(--primary-color);
}

.faq-icon {
    flex-shrink: 0;
    margin-left: var(--spacing-sm);
    transition: transform var(--transition-normal);
    stroke-width: 2.5;
}

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

.faq-answer {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.4s ease-out, padding 0.4s ease-out;
}

.faq-item.active .faq-answer {
    max-height: 500px;
    padding: 0 var(--spacing-md) var(--spacing-md);
}

.faq-answer p {
    color: var(--text-light);
    line-height: 1.8;
    margin: 0;
}

.faq-more {
    text-align: center;
    margin-top: var(--spacing-lg);
    padding: var(--spacing-md);
    background: white;
    border-radius: var(--radius-md);
    max-width: 900px;
    margin-left: auto;
    margin-right: auto;
}

.faq-more p {
    color: var(--text-light);
    font-size: var(--font-size-md);
    margin: 0;
}

/* ================================
   Footer
   ================================ */

.footer {
    background: #000;
    color: white;
    padding: var(--spacing-lg) 0 var(--spacing-md);
}

.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-md);
    padding-bottom: var(--spacing-md);
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.footer-info h3 {
    font-size: var(--font-size-lg);
    margin-bottom: var(--spacing-xs);
}

.footer-info p {
    opacity: 0.7;
    font-size: var(--font-size-xs);
}

.footer-links {
    display: flex;
    gap: var(--spacing-md);
}

.footer-links a {
    opacity: 0.8;
    transition: var(--transition-fast);
}

.footer-links a:hover {
    opacity: 1;
    color: var(--primary-color);
}

.footer-bottom {
    text-align: center;
    opacity: 0.6;
    font-size: var(--font-size-xs);
}

/* ================================
   WeChat Browser Overlay
   ================================ */

.wechat-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.95);
    z-index: 9999;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    align-items: flex-end;
    padding: 20px;
}

.wechat-overlay-content {
    display: flex;
    flex-direction: column;
    align-items: flex-end;
    margin-top: 20px;
    margin-right: 10px;
}

.wechat-arrow {
    animation: bounce-arrow 1.5s ease-in-out infinite;
    margin-bottom: 20px;
}

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

.wechat-tip {
    background: white;
    padding: 24px;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    text-align: center;
    max-width: 300px;
}

.wechat-tip-title {
    font-size: var(--font-size-lg);
    font-weight: 700;
    color: var(--text-dark);
    margin-bottom: var(--spacing-sm);
}

.wechat-tip-desc {
    font-size: var(--font-size-md);
    color: var(--text-light);
    margin: var(--spacing-xs) 0;
    line-height: 1.8;
}

.wechat-tip-desc strong {
    color: var(--primary-color);
    font-weight: 700;
    font-size: 1.2em;
}

/* ================================
   Animation Classes
   ================================ */

.fade-in,
.fade-in-up,
.fade-in-left,
.fade-in-right {
    opacity: 0;
    transition: all 0.8s ease-out;
}

.fade-in.visible {
    opacity: 1;
}

.fade-in-up {
    transform: translateY(30px);
}

.fade-in-up.visible {
    opacity: 1;
    transform: translateY(0);
    transition-delay: var(--delay, 0s);
}

.fade-in-left {
    transform: translateX(-50px);
}

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

.fade-in-right {
    transform: translateX(50px);
}

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

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

@media (max-width: 1024px) {
    :root {
        --spacing-xl: 4rem;
    }

    .feature-item,
    .feature-item-reverse {
        grid-template-columns: 1fr;
        direction: ltr;
    }

    .feature-item-reverse .feature-content {
        order: 1;
    }

    .feature-item-reverse .feature-image {
        order: 2;
    }
}

@media (max-width: 768px) {
    :root {
        --spacing-lg: 3rem;
        --spacing-xl: 3rem;
    }

    section {
        padding: var(--spacing-lg) 0;
    }

    .hero .container {
        grid-template-columns: 1fr;
        text-align: center;
    }

    .hero-icon {
        margin-left: auto;
        margin-right: auto;
    }

    .hero-cta {
        justify-content: center;
    }

    .hero-image {
        order: -1;
        max-width: 300px;
    }

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

    .footer-links {
        flex-direction: column;
        gap: var(--spacing-sm);
    }

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

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

@media (max-width: 480px) {
    .container {
        padding: 0 var(--spacing-sm);
    }

    .btn {
        padding: 0.875rem 1.5rem;
        font-size: var(--font-size-sm);
    }

    .btn-download {
        padding: 1rem 2rem;
        font-size: var(--font-size-md);
    }

    .hero-cta {
        flex-direction: column;
        width: 100%;
    }

    .hero-cta .btn {
        width: 100%;
    }

    .download-buttons {
        flex-direction: column;
        width: 100%;
        padding: 0 var(--spacing-sm);
    }

    .download-buttons .btn {
        width: 100%;
    }
}

/* ================================
   Performance Optimizations
   ================================ */

@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;
    }
}