/* ========================================
   绘影AI 首页 - 深色科技风（与客户端 UI 统一）
   设计 Token 与 app/styles.css 完全对齐
   ======================================== */

:root {
    /* 背景色系 */
    --bg-primary: #0a0a0f;
    --bg-secondary: #111118;
    --bg-tertiary: #1a1a25;
    --bg-card: #14141e;
    --bg-hover: #1e1e2e;

    /* 品牌色系 */
    --brand: #6366f1;
    --brand-light: #818cf8;
    --brand-dark: #4f46e5;
    --brand-rgb: 99, 102, 241;

    /* 渐变色 */
    --gradient-brand: linear-gradient(135deg, #4f46e5, #6366f1);
    --gradient-progress: linear-gradient(90deg, #4f46e5, #6366f1, #8b5cf6);

    /* 文本色系 */
    --text-primary: #e4e4ed;
    --text-secondary: #9ca3af;
    --text-muted: #6b7280;

    /* 语义色 */
    --success: #22c55e;
    --warning: #f59e0b;
    --error: #ef4444;

    /* 边框色 */
    --border-color: #2a2a38;

    /* 圆角 */
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 14px;

    /* 过渡 */
    --transition: 0.2s ease;

    /* 等宽字体 */
    --font-mono: 'Cascadia Code', 'Fira Code', 'JetBrains Mono', monospace;
}

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

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* ========================================
   导航栏
   ======================================== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 100;
    background: rgba(10, 10, 15, 0.88);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-bottom: 1px solid var(--border-color);
    transition: all var(--transition);
}
.navbar.scrolled {
    box-shadow: 0 2px 20px rgba(0, 0, 0, 0.4);
}
.navbar-inner {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 56px;
}
.nav-logo {
    display: flex;
    align-items: center;
    gap: 10px;
    text-decoration: none;
    color: var(--text-primary);
}
.nav-logo .logo-icon {
    width: 36px;
    height: 36px;
    background: var(--gradient-brand);
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    color: #fff;
    font-size: 18px;
    font-weight: 700;
    box-shadow: 0 2px 10px rgba(var(--brand-rgb), 0.35);
}
.nav-logo .logo-text {
    font-size: 16px;
    font-weight: 700;
    letter-spacing: 1.5px;
}
.nav-links {
    display: flex;
    gap: 28px;
    align-items: center;
    list-style: none;
}
.nav-links a {
    text-decoration: none;
    color: var(--text-secondary);
    font-size: 13px;
    font-weight: 500;
    transition: color var(--transition);
    letter-spacing: 0.3px;
}
.nav-links a:hover {
    color: var(--text-primary);
}
.nav-cta {
    background: var(--gradient-brand) !important;
    color: #fff !important;
    padding: 7px 18px !important;
    border-radius: var(--radius-sm) !important;
    font-weight: 600 !important;
    transition: all var(--transition) !important;
    box-shadow: 0 2px 10px rgba(var(--brand-rgb), 0.3) !important;
}
.nav-cta:hover {
    box-shadow: 0 4px 16px rgba(var(--brand-rgb), 0.45) !important;
    transform: translateY(-1px) !important;
    color: #fff !important;
}

/* 移动端菜单按钮 */
.nav-toggle {
    display: none;
    background: none;
    border: 1px solid var(--border-color);
    cursor: pointer;
    padding: 6px;
    border-radius: var(--radius-sm);
    transition: background var(--transition);
}
.nav-toggle:hover {
    background: var(--bg-hover);
}
.nav-toggle span {
    display: block;
    width: 20px;
    height: 2px;
    background: var(--text-primary);
    margin: 4px 0;
    transition: all 0.3s;
    border-radius: 2px;
}
@media (max-width: 768px) {
    .nav-links {
        position: fixed;
        top: 56px;
        left: 0;
        right: 0;
        background: rgba(17, 17, 24, 0.98);
        backdrop-filter: blur(16px);
        flex-direction: column;
        padding: 20px 24px;
        gap: 16px;
        transform: translateY(-120%);
        transition: transform 0.35s ease;
        border-bottom: 1px solid var(--border-color);
        box-shadow: 0 12px 40px rgba(0, 0, 0, 0.5);
    }
    .nav-links.open {
        transform: translateY(0);
    }
    .nav-toggle { display: block; }
    .nav-cta {
        width: 100%;
        text-align: center;
        justify-content: center;
    }
}

/* ========================================
   Hero 区域
   ======================================== */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    padding: 120px 24px 80px;
    position: relative;
    overflow: hidden;
    background: var(--bg-primary);
}
/* 装饰性背景光效 */
.hero::before {
    content: '';
    position: absolute;
    top: -50%;
    left: -20%;
    width: 140%;
    height: 200%;
    background:
        radial-gradient(ellipse at 25% 30%, rgba(var(--brand-rgb), 0.08) 0%, transparent 50%),
        radial-gradient(ellipse at 75% 55%, rgba(139, 92, 246, 0.06) 0%, transparent 50%),
        radial-gradient(ellipse at 50% 85%, rgba(var(--brand-rgb), 0.04) 0%, transparent 40%);
    pointer-events: none;
}
.hero-content {
    position: relative;
    z-index: 1;
    max-width: 800px;
}
.hero-badge {
    display: inline-block;
    background: rgba(var(--brand-rgb), 0.12);
    color: var(--brand-light);
    font-size: 12px;
    font-weight: 600;
    padding: 5px 14px;
    border-radius: 20px;
    margin-bottom: 24px;
    letter-spacing: 0.5px;
    border: 1px solid rgba(var(--brand-rgb), 0.2);
}
.hero h1 {
    font-size: 48px;
    font-weight: 800;
    color: var(--text-primary);
    line-height: 1.15;
    margin-bottom: 16px;
    letter-spacing: 1px;
}
.hero h1 .accent {
    color: var(--brand-light);
    position: relative;
}
.hero h1 .accent::after {
    content: '';
    position: absolute;
    bottom: 2px;
    left: 0;
    right: 0;
    height: 6px;
    background: rgba(var(--brand-rgb), 0.18);
    border-radius: 3px;
    z-index: -1;
}
.hero-subtitle {
    font-size: 16px;
    color: var(--text-secondary);
    margin-bottom: 40px;
    line-height: 1.75;
    max-width: 560px;
    margin-left: auto;
    margin-right: auto;
}
.hero-actions {
    display: flex;
    gap: 12px;
    justify-content: center;
    flex-wrap: wrap;
}

/* ===== 按钮系统（对齐客户端） ===== */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 12px 28px;
    border-radius: var(--radius-md);
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    text-decoration: none;
    border: none;
    transition: all var(--transition);
    letter-spacing: 0.3px;
    white-space: nowrap;
}
.btn-primary {
    background: var(--gradient-brand);
    color: #fff;
    box-shadow: 0 4px 20px rgba(var(--brand-rgb), 0.3);
}
.btn-primary:hover {
    box-shadow: 0 6px 28px rgba(var(--brand-rgb), 0.5);
    transform: translateY(-1px);
}
.btn-primary:active {
    transform: translateY(0);
}
.btn-outline {
    background: transparent;
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}
.btn-outline:hover {
    border-color: var(--brand);
    color: var(--brand-light);
    transform: translateY(-1px);
    box-shadow: 0 4px 16px rgba(var(--brand-rgb), 0.1);
}
.hero-version {
    margin-top: 32px;
    font-size: 13px;
    color: var(--text-muted);
}
.hero-version span {
    color: var(--brand-light);
    font-weight: 600;
}

/* Hero 展示图区域 */
.hero-visual {
    margin-top: 48px;
    position: relative;
}
.hero-visual-inner {
    position: relative;
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.5), 0 0 60px rgba(var(--brand-rgb), 0.08);
    background: var(--bg-secondary);
    aspect-ratio: 16 / 9;
    max-width: 900px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--border-color);
}
.hero-visual-placeholder {
    text-align: center;
    color: rgba(255, 255, 255, 0.15);
    padding: 40px;
}
.hero-visual-placeholder .visual-icon {
    font-size: 56px;
    display: block;
    margin-bottom: 14px;
    opacity: 0.5;
}
.hero-visual-placeholder p {
    font-size: 13px;
    letter-spacing: 2px;
    color: var(--text-muted);
}

@media (max-width: 900px) {
    .hero-visual-inner { aspect-ratio: 4 / 3; }
}
@media (max-width: 768px) {
    .hero h1 { font-size: 30px; }
    .hero-subtitle { font-size: 14px; }
    .hero-actions { flex-direction: column; align-items: center; }
    .btn { width: 100%; max-width: 280px; justify-content: center; }
    .hero-visual-inner { aspect-ratio: 3 / 4; border-radius: var(--radius-md); }
}

/* 滚动提示 */
.scroll-hint {
    position: absolute;
    bottom: 32px;
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 8px;
    animation: float 2s ease-in-out infinite;
    opacity: 0.45;
}
.scroll-hint span {
    font-size: 11px;
    color: var(--text-muted);
    letter-spacing: 2px;
    text-transform: uppercase;
}
.scroll-hint .arrow {
    width: 16px;
    height: 16px;
    border-right: 2px solid var(--text-muted);
    border-bottom: 2px solid var(--text-muted);
    transform: rotate(45deg);
}
@keyframes float {
    0%, 100% { transform: translateX(-50%) translateY(0); }
    50% { transform: translateX(-50%) translateY(6px); }
}

/* ========================================
   通用区块
   ======================================== */
.section {
    padding: 80px 24px;
    position: relative;
}
.section-inner {
    max-width: 1100px;
    margin: 0 auto;
}
.section-header {
    text-align: center;
    margin-bottom: 48px;
}
.section-header .section-icon {
    display: inline-block;
    font-size: 32px;
    margin-bottom: 12px;
    opacity: 0.7;
}
.section-header h2 {
    font-size: 28px;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 10px;
    letter-spacing: 0.5px;
}
.section-header p {
    font-size: 14px;
    color: var(--text-secondary);
    max-width: 480px;
    margin: 0 auto;
    line-height: 1.7;
}
.section-alt {
    background: var(--bg-secondary);
}

/* ========================================
   功能特性卡片
   ======================================== */
.features-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 16px;
}
.feature-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 28px 22px;
    transition: all var(--transition);
    position: relative;
    overflow: hidden;
}
.feature-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--gradient-progress);
    transform: scaleX(0);
    transition: transform 0.3s;
}
.feature-card:hover {
    transform: translateY(-2px);
    border-color: rgba(var(--brand-rgb), 0.4);
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.3), 0 0 20px rgba(var(--brand-rgb), 0.06);
}
.feature-card:hover::before {
    transform: scaleX(1);
}
.feature-icon {
    width: 44px;
    height: 44px;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 20px;
    margin-bottom: 14px;
}
.feature-icon.red    { background: rgba(239, 68, 68, 0.12); }
.feature-icon.blue   { background: rgba(var(--brand-rgb), 0.12); }
.feature-icon.green  { background: rgba(34, 197, 94, 0.12); }
.feature-icon.gold   { background: rgba(245, 158, 11, 0.12); }
.feature-icon.purple { background: rgba(139, 92, 246, 0.12); }
.feature-icon.teal   { background: rgba(20, 184, 166, 0.12); }

.feature-card h3 {
    font-size: 15px;
    font-weight: 600;
    margin-bottom: 6px;
    color: var(--text-primary);
}
.feature-card p {
    font-size: 12px;
    color: var(--text-secondary);
    line-height: 1.65;
}

@media (max-width: 900px) {
    .features-grid { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 600px) {
    .features-grid { grid-template-columns: 1fr; }
}

/* ========================================
   风格展示
   ======================================== */
.styles-grid {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 12px;
}
.style-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 20px 12px;
    text-align: center;
    transition: all var(--transition);
    cursor: default;
}
.style-card:hover {
    transform: translateY(-2px);
    border-color: rgba(var(--brand-rgb), 0.4);
    box-shadow: 0 6px 20px rgba(0, 0, 0, 0.3);
}
.style-card .style-emoji {
    font-size: 30px;
    margin-bottom: 8px;
    display: block;
}
.style-card .style-name {
    font-size: 12px;
    font-weight: 600;
    color: var(--text-secondary);
}

@media (max-width: 900px) {
    .styles-grid { grid-template-columns: repeat(3, 1fr); }
}
@media (max-width: 500px) {
    .styles-grid { grid-template-columns: repeat(2, 1fr); }
}

/* ========================================
   核心优势卡片
   ======================================== */
.advantages-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 16px;
    margin-top: 24px;
}
.advantage-card {
    text-align: center;
    padding: 28px 18px;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    transition: all var(--transition);
}
.advantage-card:hover {
    transform: translateY(-2px);
    border-color: rgba(var(--brand-rgb), 0.35);
    box-shadow: 0 8px 28px rgba(0, 0, 0, 0.35);
}
.advantage-card .adv-icon {
    font-size: 34px;
    display: block;
    margin-bottom: 10px;
    opacity: 0.8;
}
.advantage-card h4 {
    font-size: 14px;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 6px;
}
.advantage-card p {
    font-size: 12px;
    color: var(--text-secondary);
    line-height: 1.6;
}

@media (max-width: 900px) {
    .advantages-grid { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 600px) {
    .advantages-grid { grid-template-columns: 1fr; }
}

/* ========================================
   技术亮点
   ======================================== */
.highlights-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 16px;
}
.highlight-item {
    display: flex;
    gap: 14px;
    align-items: flex-start;
    padding: 22px;
    background: var(--bg-card);
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    transition: all var(--transition);
}
.highlight-item:hover {
    border-color: rgba(var(--brand-rgb), 0.3);
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.25);
}
.highlight-num {
    width: 36px;
    height: 36px;
    border-radius: var(--radius-sm);
    background: var(--gradient-brand);
    color: #fff;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 14px;
    font-weight: 700;
    flex-shrink: 0;
    box-shadow: 0 2px 8px rgba(var(--brand-rgb), 0.3);
}
.highlight-item h4 {
    font-size: 14px;
    font-weight: 600;
    margin-bottom: 4px;
    color: var(--text-primary);
}
.highlight-item p {
    font-size: 12px;
    color: var(--text-secondary);
    line-height: 1.65;
}

@media (max-width: 700px) {
    .highlights-grid { grid-template-columns: 1fr; }
}

/* ========================================
   下载区域
   ======================================== */
.download-section {
    background: var(--bg-primary);
}
.download-cards {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 16px;
    max-width: 900px;
    margin: 0 auto;
}
.download-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 32px 20px;
    text-align: center;
    transition: all var(--transition);
    position: relative;
}
.download-card:hover {
    border-color: rgba(var(--brand-rgb), 0.4);
    transform: translateY(-2px);
    box-shadow: 0 12px 40px rgba(0, 0, 0, 0.35), 0 0 30px rgba(var(--brand-rgb), 0.06);
}
.download-card.recommended {
    border-color: rgba(var(--brand-rgb), 0.5);
    box-shadow: 0 6px 24px rgba(var(--brand-rgb), 0.12);
}
.download-card .recommend-badge {
    position: absolute;
    top: -11px;
    left: 50%;
    transform: translateX(-50%);
    background: var(--gradient-brand);
    color: #fff;
    font-size: 11px;
    font-weight: 600;
    padding: 3px 14px;
    border-radius: 12px;
    white-space: nowrap;
    box-shadow: 0 2px 8px rgba(var(--brand-rgb), 0.35);
    letter-spacing: 0.3px;
}
.download-os-icon {
    font-size: 40px;
    margin-bottom: 14px;
    display: block;
    opacity: 0.8;
}
.download-card h3 {
    font-size: 16px;
    font-weight: 700;
    margin-bottom: 4px;
    color: var(--text-primary);
}
.download-card .dl-arch {
    font-size: 12px;
    color: var(--text-muted);
    margin-bottom: 10px;
}
.download-card .dl-size {
    font-size: 12px;
    color: var(--text-secondary);
    margin-bottom: 18px;
    padding: 3px 10px;
    background: var(--bg-secondary);
    border-radius: var(--radius-sm);
    display: inline-block;
    font-family: var(--font-mono);
}
.download-card .btn-dl {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 10px 24px;
    background: var(--gradient-brand);
    color: #fff;
    border-radius: var(--radius-md);
    text-decoration: none;
    font-size: 13px;
    font-weight: 600;
    transition: all var(--transition);
    box-shadow: 0 2px 12px rgba(var(--brand-rgb), 0.3);
}
.download-card .btn-dl:hover {
    box-shadow: 0 4px 20px rgba(var(--brand-rgb), 0.5);
    transform: translateY(-1px);
}
.download-card.recommended .btn-dl {
    box-shadow: 0 4px 18px rgba(var(--brand-rgb), 0.35);
}
.download-version-info {
    text-align: center;
    margin-bottom: 28px;
    color: var(--text-muted);
    font-size: 13px;
}
.download-version-info strong {
    color: var(--text-primary);
}

@media (max-width: 800px) {
    .download-cards { grid-template-columns: 1fr; max-width: 340px; }
}

/* ========================================
   兼容提示
   ======================================== */
.compat-note {
    text-align: center;
    margin-top: 14px;
    font-size: 12px;
    color: var(--text-muted);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    flex-wrap: wrap;
}
.compat-note .sep {
    color: var(--border-color);
}

/* ========================================
   使用步骤
   ======================================== */
.steps {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 16px;
    position: relative;
}
.step-card {
    text-align: center;
    position: relative;
}
.step-number {
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: var(--gradient-brand);
    color: #fff;
    font-size: 20px;
    font-weight: 700;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 14px;
    box-shadow: 0 4px 16px rgba(var(--brand-rgb), 0.35);
}
.step-card h4 {
    font-size: 14px;
    font-weight: 600;
    margin-bottom: 6px;
    color: var(--text-primary);
}
.step-card p {
    font-size: 12px;
    color: var(--text-secondary);
    line-height: 1.65;
}
.step-card:not(:last-child)::after {
    content: '';
    position: absolute;
    top: 24px;
    right: -8px;
    width: 16px;
    height: 1px;
    background: var(--border-color);
}

@media (max-width: 800px) {
    .steps { grid-template-columns: repeat(2, 1fr); }
    .step-card:nth-child(2)::after { display: none; }
}
@media (max-width: 500px) {
    .steps { grid-template-columns: 1fr; }
    .step-card::after { display: none !important; }
}

/* ========================================
   更新日志
   ======================================== */
.changelog-list {
    max-width: 640px;
    margin: 0 auto;
}
.changelog-item {
    display: flex;
    gap: 12px;
    padding: 10px 0;
    border-bottom: 1px solid var(--border-color);
}
.changelog-item:last-child {
    border-bottom: none;
}
.changelog-dot {
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--brand);
    flex-shrink: 0;
    margin-top: 7px;
}
.changelog-text {
    font-size: 13px;
    color: var(--text-secondary);
    line-height: 1.65;
}

/* ========================================
   系统要求表格
   ======================================== */
.req-table-wrap {
    max-width: 640px;
    margin: 0 auto;
    overflow-x: auto;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
}
.req-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 13px;
}
.req-table th,
.req-table td {
    padding: 10px 14px;
    text-align: left;
    border-bottom: 1px solid var(--border-color);
}
.req-table th {
    font-weight: 600;
    color: var(--text-muted);
    font-size: 11px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    background: var(--bg-secondary);
}
.req-table tbody tr:last-child td {
    border-bottom: none;
}
.req-table td {
    color: var(--text-secondary);
    background: var(--bg-card);
}
.req-table .tag {
    display: inline-block;
    padding: 2px 8px;
    border-radius: 4px;
    font-size: 11px;
    font-weight: 600;
}
.tag-green  { background: rgba(34, 197, 94, 0.12); color: var(--success); }
.tag-yellow { background: rgba(245, 158, 11, 0.12); color: var(--warning); }
.tag-red    { background: rgba(239, 68, 68, 0.12); color: var(--error); }

/* ========================================
   页脚
   ======================================== */
.footer {
    background: var(--bg-secondary);
    border-top: 1px solid var(--border-color);
    padding: 44px 24px 28px;
    text-align: center;
}
.footer-inner {
    max-width: 1100px;
    margin: 0 auto;
}
.footer-logo {
    font-size: 18px;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 6px;
    letter-spacing: 1.5px;
}
.footer-tagline {
    font-size: 12px;
    margin-bottom: 20px;
    color: var(--text-muted);
}
.footer-links {
    display: flex;
    gap: 20px;
    justify-content: center;
    margin-bottom: 20px;
    flex-wrap: wrap;
}
.footer-links a {
    color: var(--text-muted);
    text-decoration: none;
    font-size: 12px;
    transition: color var(--transition);
}
.footer-links a:hover {
    color: var(--brand-light);
}
.footer-divider {
    width: 48px;
    height: 1px;
    background: var(--border-color);
    margin: 0 auto 20px;
}
.footer-copyright {
    font-size: 11px;
    color: rgba(255, 255, 255, 0.15);
}

/* ========================================
   动画
   ======================================== */
.fade-in {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.5s ease, transform 0.5s ease;
}
.fade-in.visible {
    opacity: 1;
    transform: translateY(0);
}
.delay-1 { transition-delay: 0.08s; }
.delay-2 { transition-delay: 0.16s; }
.delay-3 { transition-delay: 0.24s; }
.delay-4 { transition-delay: 0.32s; }

/* ========================================
   回到顶部按钮
   ======================================== */
.back-to-top {
    position: fixed;
    bottom: 28px;
    right: 28px;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: var(--bg-hover);
    color: var(--text-secondary);
    border: 1px solid var(--border-color);
    cursor: pointer;
    font-size: 18px;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    transform: translateY(16px);
    transition: all var(--transition);
    pointer-events: none;
    z-index: 50;
}
.back-to-top.visible {
    opacity: 1;
    transform: translateY(0);
    pointer-events: auto;
}
.back-to-top:hover {
    background: var(--brand);
    color: #fff;
    border-color: var(--brand);
    box-shadow: 0 4px 16px rgba(var(--brand-rgb), 0.4);
    transform: translateY(-2px);
}

/* ========================================
   Toast 提示
   ======================================== */
.toast {
    position: fixed;
    top: 72px;
    left: 50%;
    transform: translateX(-50%);
    z-index: 300;
    padding: 8px 20px;
    border-radius: var(--radius-sm);
    color: #fff;
    font-size: 13px;
    font-weight: 500;
    background: var(--bg-hover);
    border: 1px solid var(--border-color);
    opacity: 0;
    transition: opacity 0.3s;
    pointer-events: none;
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.4);
}
.toast.show {
    opacity: 1;
}