/* ============================================
   快手 App 下载 - 完整样式
   配色：快手红 + 渐变紫橙 + 亮白
   包含：管理后台样式
   ============================================ */

/* ---------- CSS Variables ---------- */
:root {
    --primary: #ff6b35;
    --primary-dark: #e55a2b;
    --secondary: #ff2d55;
    --accent: #ff9500;
    --gradient: linear-gradient(135deg, #ff6b35, #ff2d55);
    --gradient-alt: linear-gradient(135deg, #ff2d55, #ff9500);
    --text-dark: #1a1a2e;
    --text-muted: #6b7280;
    --bg-light: #f9fafb;
    --bg-white: #ffffff;
    --shadow: 0 4px 24px rgba(0, 0, 0, 0.08);
    --shadow-hover: 0 8px 40px rgba(255, 45, 85, 0.2);
    --radius: 16px;
    --radius-sm: 10px;
    --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    --font: 'PingFang SC', 'Microsoft YaHei', system-ui, -apple-system, sans-serif;
}

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

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

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

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

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

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

/* ---------- Header ---------- */
.site-header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    z-index: 1000;
    padding: 16px 0;
    transition: var(--transition);
    background: transparent;
}

.site-header.scrolled {
    background: rgba(255, 255, 255, 0.92);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    box-shadow: 0 2px 20px rgba(0, 0, 0, 0.06);
    padding: 10px 0;
}

.header-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 22px;
    font-weight: 800;
    color: var(--text-dark);
}

.logo-icon {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    background: var(--gradient);
    border-radius: 10px;
    color: #fff;
    font-size: 18px;
    box-shadow: 0 4px 12px rgba(255, 45, 85, 0.3);
}

.logo-text {
    background: var(--gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.main-nav {
    display: flex;
    align-items: center;
    gap: 8px;
}

.nav-link {
    padding: 8px 18px;
    border-radius: 30px;
    font-size: 15px;
    font-weight: 500;
    color: var(--text-muted);
    transition: var(--transition);
    position: relative;
}

.nav-link:hover,
.nav-link.active {
    color: var(--primary);
    background: rgba(255, 107, 53, 0.08);
}

.nav-link.active {
    font-weight: 600;
}

/* ---------- Menu Toggle ---------- */
.menu-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
}

.menu-toggle span {
    display: block;
    width: 26px;
    height: 2.5px;
    background: var(--text-dark);
    border-radius: 2px;
    transition: var(--transition);
}

.menu-toggle.active span:nth-child(1) {
    transform: rotate(45deg) translate(5px, 5px);
}

.menu-toggle.active span:nth-child(2) {
    opacity: 0;
}

.menu-toggle.active span:nth-child(3) {
    transform: rotate(-45deg) translate(5px, -5px);
}

/* ---------- Hero ---------- */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    background: linear-gradient(160deg, #fff5f0 0%, #fff0f3 50%, #fef3e7 100%);
    padding: 120px 0 80px;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -20%;
    width: 600px;
    height: 600px;
    background: radial-gradient(circle, rgba(255, 107, 53, 0.08), transparent 70%);
    border-radius: 50%;
    pointer-events: none;
}

.hero-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 60px;
    align-items: center;
    position: relative;
    z-index: 1;
}

.hero-text h1 {
    font-size: 56px;
    font-weight: 800;
    line-height: 1.15;
    margin-bottom: 20px;
    color: var(--text-dark);
}

.highlight {
    background: var(--gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-text p {
    font-size: 18px;
    color: var(--text-muted);
    margin-bottom: 32px;
    max-width: 500px;
}

.hero-download {
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
    margin-bottom: 24px;
}

/* ---------- Download Buttons ---------- */
.download-btn {
    display: inline-flex;
    align-items: center;
    gap: 12px;
    padding: 14px 28px;
    border-radius: 50px;
    font-size: 16px;
    font-weight: 600;
    transition: var(--transition);
    cursor: pointer;
    border: none;
}

.android-btn {
    background: var(--gradient);
    color: #fff;
    box-shadow: 0 4px 20px rgba(255, 45, 85, 0.35);
}

.android-btn:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 30px rgba(255, 45, 85, 0.45);
}

.ios-btn {
    background: var(--text-dark);
    color: #fff;
    box-shadow: 0 4px 20px rgba(26, 26, 46, 0.2);
}

.ios-btn:hover {
    transform: translateY(-3px);
    background: #2a2a4e;
    box-shadow: 0 8px 30px rgba(26, 26, 46, 0.3);
}

.btn-icon {
    font-size: 24px;
}

.btn-text {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    line-height: 1.3;
}

.btn-text small {
    font-size: 11px;
    font-weight: 400;
    opacity: 0.85;
}

.btn-text strong {
    font-size: 17px;
}

.hero-stats {
    display: flex;
    gap: 20px;
    font-size: 14px;
    color: var(--text-muted);
}

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

.phone-mockup {
    width: 280px;
    height: 560px;
    background: var(--text-dark);
    border-radius: 40px;
    padding: 12px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.15), 0 0 0 1px rgba(255, 255, 255, 0.1);
    position: relative;
}

.phone-screen {
    width: 100%;
    height: 100%;
    background: #fff;
    border-radius: 30px;
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.app-interface {
    flex: 1;
    display: flex;
    flex-direction: column;
}

.app-header {
    background: var(--gradient);
    color: #fff;
    padding: 14px 20px;
    font-weight: 700;
    font-size: 16px;
}

.app-content {
    flex: 1;
    padding: 12px;
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.feed-item {
    background: #f0f0f0;
    border-radius: 12px;
    height: 80px;
    animation: shimmer 1.5s infinite ease-in-out;
}

.feed-item:nth-child(2) {
    height: 100px;
}

.feed-item:nth-child(3) {
    height: 60px;
}

@keyframes shimmer {
    0%, 100% { opacity: 0.5; }
    50% { opacity: 0.8; }
}

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

.section-title {
    text-align: center;
    font-size: 36px;
    font-weight: 800;
    margin-bottom: 60px;
    color: var(--text-dark);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 30px;
}

.feature-card {
    background: var(--bg-light);
    border-radius: var(--radius);
    padding: 36px 28px;
    text-align: center;
    transition: var(--transition);
    border: 1px solid transparent;
}

.feature-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-hover);
    border-color: rgba(255, 107, 53, 0.15);
}

.feature-icon {
    font-size: 48px;
    margin-bottom: 20px;
}

.feature-card h3 {
    font-size: 20px;
    font-weight: 700;
    margin-bottom: 12px;
}

.feature-card p {
    color: var(--text-muted);
    font-size: 15px;
    line-height: 1.7;
}

/* ---------- FAQ ---------- */
.faq {
    padding: 100px 0;
    background: linear-gradient(160deg, #fef3e7 0%, #fff5f0 100%);
}

.faq-list {
    max-width: 720px;
    margin: 0 auto;
}

.faq-item {
    background: #fff;
    border-radius: var(--radius-sm);
    margin-bottom: 12px;
    overflow: hidden;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.04);
    transition: var(--transition);
}

.faq-item:hover {
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.06);
}

.faq-question {
    width: 100%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 18px 24px;
    background: none;
    border: none;
    font-size: 16px;
    font-weight: 600;
    color: var(--text-dark);
    cursor: pointer;
    transition: var(--transition);
    text-align: left;
}

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

.faq-arrow {
    font-size: 12px;
    transition: var(--transition);
    color: var(--text-muted);
}

.faq-item.open .faq-arrow {
    transform: rotate(180deg);
    color: var(--primary);
}

.faq-answer {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.4s ease, padding 0.4s ease;
    padding: 0 24px;
}

.faq-item.open .faq-answer {
    max-height: 300px;
    padding: 0 24px 20px;
}

.faq-answer p {
    color: var(--text-muted);
    font-size: 15px;
    line-height: 1.8;
}

/* ---------- Download CTA ---------- */
.download-cta {
    padding: 100px 0;
    background: var(--text-dark);
    text-align: center;
    color: #fff;
}

.download-cta h2 {
    font-size: 40px;
    font-weight: 800;
    margin-bottom: 16px;
}

.download-cta p {
    font-size: 18px;
    color: rgba(255, 255, 255, 0.7);
    margin-bottom: 40px;
}

.cta-buttons {
    display: flex;
    justify-content: center;
    gap: 20px;
    flex-wrap: wrap;
}

/* ---------- Footer ---------- */
.site-footer {
    background: #111;
    color: rgba(255, 255, 255, 0.7);
    padding: 40px 0;
}

.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 20px;
}

.footer-brand {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 18px;
    font-weight: 700;
    color: #fff;
}

.footer-links {
    display: flex;
    gap: 24px;
    font-size: 14px;
}

.footer-links a {
    transition: color 0.3s;
}

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

.footer-copyright {
    font-size: 13px;
}

/* ---------- Back to Top ---------- */
.back-to-top {
    position: fixed;
    bottom: 80px;
    right: 24px;
    z-index: 999;
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: var(--gradient);
    color: #fff;
    border: none;
    font-size: 22px;
    cursor: pointer;
    box-shadow: 0 4px 16px rgba(255, 45, 85, 0.3);
    transition: var(--transition);
    opacity: 0;
    visibility: hidden;
    transform: translateY(20px);
    display: flex;
    align-items: center;
    justify-content: center;
}

.back-to-top.visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.back-to-top:hover {
    transform: translateY(-4px);
    box-shadow: 0 6px 24px rgba(255, 45, 85, 0.4);
}

/* ---------- Responsive ---------- */
@media (max-width: 1024px) {
    .hero-content {
        grid-template-columns: 1fr;
        text-align: center;
    }
    .hero-text p {
        margin: 0 auto 32px;
    }
    .hero-download {
        justify-content: center;
    }
    .hero-stats {
        justify-content: center;
    }
    .hero-visual {
        display: none;
    }
    .hero-text h1 {
        font-size: 42px;
    }
}

@media (max-width: 768px) {
    .menu-toggle {
        display: flex;
    }
    .main-nav {
        position: fixed;
        top: 0;
        right: -100%;
        width: 280px;
        height: 100vh;
        background: #fff;
        flex-direction: column;
        padding: 80px 30px 30px;
        box-shadow: -4px 0 30px rgba(0, 0, 0, 0.1);
        transition: right 0.4s ease;
        gap: 4px;
        align-items: stretch;
    }
    .main-nav.open {
        right: 0;
    }
    .nav-link {
        padding: 14px 20px;
        border-radius: 12px;
        font-size: 17px;
    }
    .hero-text h1 {
        font-size: 32px;
    }
    .section-title {
        font-size: 28px;
    }
    .features-grid {
        grid-template-columns: 1fr;
    }
    .footer-content {
        flex-direction: column;
        text-align: center;
    }
    .footer-links {
        justify-content: center;
        flex-wrap: wrap;
    }
    .back-to-top {
        bottom: 24px;
        right: 16px;
        width: 42px;
        height: 42px;
        font-size: 18px;
    }
    .download-btn {
        width: 100%;
        justify-content: center;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 16px;
    }
    .hero-text h1 {
        font-size: 28px;
    }
    .hero-stats {
        flex-direction: column;
        gap: 6px;
    }
    .download-cta h2 {
        font-size: 28px;
    }
}

/* ---------- No Scroll ---------- */
body.no-scroll {
    overflow: hidden;
}

/* ---------- Selection ---------- */
::selection {
    background: rgba(255, 107, 53, 0.25);
    color: var(--text-dark);
}

/* ---------- 管理后台样式（已移入 admin.html 内部） ---------- */
/* 此文件不再包含管理后台样式，统一由 admin.html 管理 */

【特色】分类：下载站；架构：纯静态；本次修改：新增完整管理后台页面；修改文件：admin.html, index.html, script.js, style.css；主要变化：添加 admin.html 管理后台，包含登录验证、下载链接管理、公告管理、系统设置、数据统计等功能；在 index.html 中添加公告栏、管理后台入口按钮，并实现与后台的跨页面通信同步设置；更新 script.js 和 style.css 以支持新功能