/* =============== 
   CSS Variables (Design Tokens) 
   =============== */
:root {
    --primary-color: #E60012; /* 网易红/有道红 典型主色调 */
    --primary-hover: #CC0010;
    --secondary-color: #F8F9FA;
    --text-color: #333333;
    --text-light: #666666;
    --text-muted: #999999;
    --bg-color: #FFFFFF;
    --bg-light: #F5F7FA;
    --border-color: #E5E7EB;
    
    --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", "PingFang SC", "Microsoft YaHei", sans-serif;
    
    --container-width: 1200px;
    --border-radius-sm: 8px;
    --border-radius-md: 12px;
    --border-radius-lg: 24px;
    
    --shadow-sm: 0 2px 8px rgba(0,0,0,0.05);
    --shadow-md: 0 8px 24px rgba(0,0,0,0.08);
    --shadow-lg: 0 16px 48px rgba(0,0,0,0.12);
    
    --transition: all 0.3s ease;
}

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

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

body {
    font-family: var(--font-family);
    color: var(--text-color);
    background-color: var(--bg-color);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

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

ul {
    list-style: none;
}

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

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

.container {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 24px;
}

/* =============== 
   Typography 
   =============== */
h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.2;
    color: var(--text-color);
}

.highlight {
    color: var(--primary-color);
}

/* =============== 
   Buttons 
   =============== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 10px 24px;
    border-radius: var(--border-radius-sm);
    font-weight: 500;
    font-size: 1rem;
    cursor: pointer;
    border: none;
    transition: var(--transition);
}

.btn-icon {
    margin-right: 8px;
}

.btn-primary {
    background-color: var(--primary-color);
    color: #fff;
}

.btn-primary:hover {
    background-color: var(--primary-hover);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(230, 0, 18, 0.3);
}

.btn-secondary {
    background-color: var(--bg-color);
    color: var(--text-color);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover {
    background-color: var(--bg-light);
    transform: translateY(-2px);
    box-shadow: var(--shadow-sm);
}

.btn-large {
    padding: 14px 32px;
    font-size: 1.125rem;
    border-radius: var(--border-radius-md);
}

.btn-full {
    width: 100%;
}

/* =============== 
   Header / Navbar 
   =============== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    background-color: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
    height: 72px;
    display: flex;
    align-items: center;
}

.nav-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    width: 100%;
}

.logo img {
    height: 40px;
}

.nav-links {
    display: flex;
    gap: 32px;
}

.nav-links a {
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-color);
    position: relative;
}

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

.nav-links a::after {
    content: '';
    position: absolute;
    bottom: -6px;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--primary-color);
    transition: var(--transition);
}

.nav-links a:hover::after,
.nav-links a.active::after {
    width: 100%;
}

.mobile-menu-btn {
    display: none;
    background: none;
    border: none;
    color: var(--text-color);
    cursor: pointer;
}

/* =============== 
   Hero Section 
   =============== */
.hero {
    padding: 160px 0 80px;
    background: linear-gradient(135deg, #FFF0F1 0%, #FFFFFF 100%);
    overflow: hidden;
}

.hero-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 40px;
}

.hero-text {
    flex: 1;
    max-width: 600px;
}

.hero-title {
    font-size: 3.5rem;
    margin-bottom: 24px;
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--text-light);
    margin-bottom: 40px;
}

.hero-buttons {
    display: flex;
    gap: 16px;
    margin-bottom: 48px;
}

.hero-stats {
    display: flex;
    gap: 40px;
}

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

.stat-item strong {
    font-size: 1.75rem;
    color: var(--text-color);
    line-height: 1.2;
}

.stat-item span {
    font-size: 0.875rem;
    color: var(--text-light);
    margin-top: 4px;
}

.hero-image {
    flex: 1;
    position: relative;
    display: flex;
    justify-content: flex-end;
}

.hero-image img {
    max-width: 120%;
    margin-right: -10%;
    filter: drop-shadow(0 20px 40px rgba(0,0,0,0.1));
    animation: float 6s ease-in-out infinite;
}

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

/* =============== 
   Features Section 
   =============== */
.features {
    padding: 100px 0;
    background-color: var(--bg-color);
}

.section-header {
    text-align: center;
    margin-bottom: 64px;
}

.section-title {
    font-size: 2.5rem;
    margin-bottom: 16px;
}

.section-desc {
    font-size: 1.125rem;
    color: var(--text-light);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 32px;
}

.feature-card {
    padding: 40px 32px;
    background-color: var(--bg-light);
    border-radius: var(--border-radius-lg);
    transition: var(--transition);
    text-align: center;
    border: 1px solid transparent;
}

.feature-card:hover {
    transform: translateY(-8px);
    background-color: var(--bg-color);
    border-color: var(--border-color);
    box-shadow: var(--shadow-md);
}

.feature-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto 24px;
    background-color: #FFF0F1;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--primary-color);
}

.feature-title {
    font-size: 1.25rem;
    margin-bottom: 16px;
}

.feature-desc {
    color: var(--text-light);
    font-size: 0.9375rem;
}

/* =============== 
   Download Section 
   =============== */
.download-section {
    padding: 100px 0;
    background-color: var(--bg-light);
}

.download-content {
    text-align: center;
    max-width: 1000px;
    margin: 0 auto;
}

.download-title {
    font-size: 2.5rem;
    margin-bottom: 16px;
}

.download-desc {
    font-size: 1.125rem;
    color: var(--text-light);
    margin-bottom: 64px;
}

.download-options {
    display: flex;
    justify-content: center;
    gap: 32px;
}

.download-card {
    flex: 1;
    max-width: 320px;
    background-color: var(--bg-color);
    padding: 40px;
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
}

.download-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-md);
}

.platform-icon {
    width: 64px;
    height: 64px;
    margin: 0 auto 24px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #333;
}

.platform-icon.windows { color: #0078D7; }
.platform-icon.mac { color: #333; }
.platform-icon.mobile { color: #4CAF50; }

.download-card h3 {
    font-size: 1.5rem;
    margin-bottom: 8px;
}

.download-card p {
    color: var(--text-light);
    margin-bottom: 32px;
}

.qr-code-placeholder {
    margin-bottom: 24px;
    display: flex;
    justify-content: center;
}

/* =============== 
   Footer 
   =============== */
.footer {
    background-color: #212529;
    color: #fff;
    padding-top: 80px;
}

.footer-content {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1fr;
    gap: 40px;
    margin-bottom: 64px;
}

.footer-logo {
    display: block;
    margin-bottom: 24px;
    filter: brightness(0) invert(1);
}

.footer-desc {
    color: #ADB5BD;
    font-size: 0.9375rem;
    max-width: 300px;
}

.footer-col h4 {
    color: #fff;
    font-size: 1.125rem;
    margin-bottom: 24px;
}

.footer-col ul li {
    margin-bottom: 12px;
}

.footer-col a {
    color: #ADB5BD;
    font-size: 0.9375rem;
}

.footer-col a:hover {
    color: #fff;
}

.footer-bottom {
    border-top: 1px solid rgba(255,255,255,0.1);
    padding: 24px 0;
    text-align: center;
    color: #6C757D;
    font-size: 0.875rem;
}

/* =============== 
   Responsive 
   =============== */
@media (max-width: 992px) {
    .hero-container {
        flex-direction: column;
        text-align: center;
    }
    
    .hero-text {
        max-width: 100%;
    }
    
    .hero-buttons, .hero-stats {
        justify-content: center;
    }
    
    .hero-image {
        justify-content: center;
        margin-top: 40px;
    }
    
    .hero-image img {
        margin-right: 0;
        max-width: 100%;
    }
    
    .features-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .download-options {
        flex-wrap: wrap;
    }
    
    .footer-content {
        grid-template-columns: 1fr 1fr;
    }
}

@media (max-width: 768px) {
    .nav-links, .nav-actions {
        display: none;
    }
    
    .mobile-menu-btn {
        display: block;
    }
    
    .hero-title {
        font-size: 2.5rem;
    }
    
    .hero-buttons {
        flex-direction: column;
    }
    
    .btn-large {
        width: 100%;
    }
    
    .features-grid {
        grid-template-columns: 1fr;
    }
    
    .footer-content {
        grid-template-columns: 1fr;
    }
}