/* ===== 全局重置与基础变量 ===== */
*,
*::before,
*::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    /* 主色调 — 深蓝 + 米兰红 */
    --color-primary: #0a0a23;
    --color-primary-light: #1a1a3e;
    --color-accent: #e63946;
    --color-accent-hover: #ff4d5a;
    --color-accent-soft: rgba(230, 57, 70, 0.12);
    --color-bg: #f8f9fa;
    --color-surface: #ffffff;
    --color-surface-glass: rgba(255, 255, 255, 0.55);
    --color-text: #1e1e2f;
    --color-text-secondary: #4a4a5e;
    --color-border: #e0e0e8;
    --color-shadow: rgba(10, 10, 35, 0.08);
    --color-hero-gradient: linear-gradient(135deg, #0a0a23 0%, #1a1a3e 50%, #e63946 100%);
    --radius-sm: 8px;
    --radius-md: 16px;
    --radius-lg: 24px;
    --radius-xl: 32px;
    --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    --font-sans: 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', system-ui, -apple-system, sans-serif;
    --max-width: 1200px;
    --nav-height: 64px;
    --scroll-offset: 80px;
}

/* 暗色模式变量 */
body.dark-mode {
    --color-primary: #0d0d2b;
    --color-primary-light: #1a1a40;
    --color-bg: #12121a;
    --color-surface: #1c1c2e;
    --color-surface-glass: rgba(28, 28, 46, 0.65);
    --color-text: #e8e8f0;
    --color-text-secondary: #a0a0b8;
    --color-border: #2a2a40;
    --color-shadow: rgba(0, 0, 0, 0.4);
    --color-accent-soft: rgba(230, 57, 70, 0.18);
}

html {
    scroll-behavior: smooth;
    -webkit-text-size-adjust: 100%;
}

body {
    font-family: var(--font-sans);
    background: var(--color-bg);
    color: var(--color-text);
    line-height: 1.6;
    min-height: 100vh;
    transition: background var(--transition), color var(--transition);
}

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

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

a:hover, a:focus-visible {
    color: var(--color-accent-hover);
}

ul, ol {
    list-style: none;
}

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

h1 { font-size: clamp(2rem, 5vw, 3.2rem); }
h2 { font-size: clamp(1.6rem, 3.5vw, 2.4rem); margin-bottom: 1.5rem; }
h3 { font-size: 1.2rem; margin-bottom: 0.75rem; }

p {
    margin-bottom: 1rem;
    color: var(--color-text-secondary);
}

/* ===== 容器 ===== */
.nav-container,
main > section,
.footer-content {
    max-width: var(--max-width);
    margin: 0 auto;
    padding-left: 1.5rem;
    padding-right: 1.5rem;
}

/* ===== Header / Navigation ===== */
header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    z-index: 1000;
    background: var(--color-surface-glass);
    backdrop-filter: blur(16px) saturate(180%);
    -webkit-backdrop-filter: blur(16px) saturate(180%);
    border-bottom: 1px solid var(--color-border);
    transition: background var(--transition), border-color var(--transition);
    height: var(--nav-height);
}

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

.logo {
    display: flex;
    align-items: center;
    flex-shrink: 0;
}

.logo svg {
    height: 36px;
    width: auto;
}

.nav-links {
    display: flex;
    gap: 0.25rem;
    margin: 0;
    padding: 0;
}

.nav-links li a {
    display: inline-block;
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
    font-weight: 500;
    font-size: 0.95rem;
    color: var(--color-text);
    transition: background var(--transition), color var(--transition);
    position: relative;
}

.nav-links li a:hover,
.nav-links li a:focus-visible {
    background: var(--color-accent-soft);
    color: var(--color-accent);
}

.nav-links li a[aria-current="page"] {
    color: var(--color-accent);
    background: var(--color-accent-soft);
}

/* 暗色模式 & 移动菜单按钮 */
.dark-mode-toggle,
.mobile-menu-toggle {
    background: transparent;
    border: none;
    cursor: pointer;
    padding: 0.5rem;
    border-radius: var(--radius-sm);
    color: var(--color-text);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background var(--transition), color var(--transition);
}

.dark-mode-toggle:hover,
.mobile-menu-toggle:hover {
    background: var(--color-accent-soft);
    color: var(--color-accent);
}

.mobile-menu-toggle {
    display: none;
    flex-direction: column;
    gap: 4px;
    width: 36px;
    height: 36px;
}

.mobile-menu-toggle span {
    display: block;
    width: 22px;
    height: 2px;
    background: var(--color-text);
    border-radius: 2px;
    transition: all var(--transition);
}

.mobile-menu-toggle[aria-expanded="true"] span:nth-child(1) {
    transform: rotate(45deg) translate(4px, 4px);
}

.mobile-menu-toggle[aria-expanded="true"] span:nth-child(2) {
    opacity: 0;
}

.mobile-menu-toggle[aria-expanded="true"] span:nth-child(3) {
    transform: rotate(-45deg) translate(4px, -4px);
}

/* ===== Hero Section ===== */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: calc(var(--nav-height) + 2rem) 1.5rem 4rem;
    background: var(--color-hero-gradient);
    position: relative;
    overflow: hidden;
    text-align: center;
}

.hero::before {
    content: '';
    position: absolute;
    inset: 0;
    background: radial-gradient(circle at 70% 30%, rgba(230, 57, 70, 0.15) 0%, transparent 60%),
                radial-gradient(circle at 20% 70%, rgba(10, 10, 35, 0.4) 0%, transparent 50%);
    pointer-events: none;
}

.hero-content {
    position: relative;
    z-index: 2;
    max-width: 720px;
}

.hero-content h1 {
    font-size: clamp(2.2rem, 6vw, 3.8rem);
    color: #ffffff;
    margin-bottom: 1rem;
    text-shadow: 0 2px 20px rgba(0,0,0,0.3);
}

.hero-content p {
    font-size: 1.2rem;
    color: rgba(255,255,255,0.85);
    margin-bottom: 2rem;
}

.hero-actions {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.8rem 2rem;
    border-radius: var(--radius-xl);
    font-weight: 600;
    font-size: 1rem;
    transition: all var(--transition);
    border: 2px solid transparent;
    cursor: pointer;
}

.btn-primary {
    background: var(--color-accent);
    color: #ffffff;
    border-color: var(--color-accent);
}

.btn-primary:hover {
    background: var(--color-accent-hover);
    border-color: var(--color-accent-hover);
    transform: translateY(-2px);
    box-shadow: 0 8px 24px rgba(230, 57, 70, 0.35);
}

.btn-secondary {
    background: transparent;
    color: #ffffff;
    border-color: rgba(255,255,255,0.6);
}

.btn-secondary:hover {
    background: rgba(255,255,255,0.1);
    border-color: #ffffff;
    transform: translateY(-2px);
}

.hero-visual {
    position: absolute;
    right: 5%;
    bottom: 5%;
    opacity: 0.2;
    pointer-events: none;
    z-index: 1;
}

.hero-visual svg {
    width: clamp(200px, 40vw, 400px);
    height: auto;
}

/* ===== Sections 通用 ===== */
main > section {
    padding: 5rem 1.5rem;
}

section:nth-child(even) {
    background: var(--color-surface);
}

section h2 {
    text-align: center;
    position: relative;
    display: inline-block;
    left: 50%;
    transform: translateX(-50%);
    margin-bottom: 2.5rem;
}

section h2::after {
    content: '';
    display: block;
    width: 60px;
    height: 4px;
    background: var(--color-accent);
    border-radius: 4px;
    margin: 0.75rem auto 0;
}

/* ===== About Grid ===== */
.about-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 1.5rem;
}

.about-grid article {
    background: var(--color-surface);
    border-radius: var(--radius-md);
    padding: 1.75rem;
    box-shadow: 0 4px 20px var(--color-shadow);
    border: 1px solid var(--color-border);
    transition: all var(--transition);
}

.about-grid article:hover {
    transform: translateY(-6px);
    box-shadow: 0 12px 36px var(--color-shadow);
    border-color: var(--color-accent);
}

.about-grid h3 {
    color: var(--color-accent);
}

/* ===== Card Grid ===== */
.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 1.5rem;
}

.card {
    background: var(--color-surface);
    border-radius: var(--radius-md);
    padding: 2rem 1.5rem;
    box-shadow: 0 4px 20px var(--color-shadow);
    border: 1px solid var(--color-border);
    transition: all var(--transition);
    position: relative;
    overflow: hidden;
}

.card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 4px;
    background: var(--color-accent);
    transform: scaleX(0);
    transform-origin: left;
    transition: transform 0.4s ease;
}

.card:hover::before {
    transform: scaleX(1);
}

.card:hover {
    transform: translateY(-6px) scale(1.01);
    box-shadow: 0 16px 40px var(--color-shadow);
    border-color: var(--color-accent);
}

.card h3 {
    color: var(--color-text);
    margin-bottom: 0.75rem;
}

.card p {
    font-size: 0.95rem;
}

.card a {
    display: inline-block;
    margin-top: 0.75rem;
    font-weight: 600;
}

/* ===== Feature List ===== */
.feature-list {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 1.25rem;
}

.feature-list li {
    background: var(--color-surface);
    padding: 1.5rem;
    border-radius: var(--radius-md);
    border: 1px solid var(--color-border);
    box-shadow: 0 2px 12px var(--color-shadow);
    transition: all var(--transition);
}

.feature-list li:hover {
    transform: translateY(-4px);
    box-shadow: 0 8px 28px var(--color-shadow);
    border-color: var(--color-accent);
}

.feature-list strong {
    color: var(--color-accent);
}

/* ===== Testimonials ===== */
.testimonial-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

blockquote {
    background: var(--color-surface);
    border-radius: var(--radius-md);
    padding: 2rem;
    border-left: 4px solid var(--color-accent);
    box-shadow: 0 4px 20px var(--color-shadow);
    transition: all var(--transition);
}

blockquote:hover {
    transform: translateY(-4px);
    box-shadow: 0 12px 32px var(--color-shadow);
}

blockquote p {
    font-style: italic;
    font-size: 1.05rem;
    margin-bottom: 1rem;
}

blockquote footer {
    font-weight: 600;
    color: var(--color-accent);
}

/* ===== FAQ ===== */
.faq-list {
    max-width: 800px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

details {
    background: var(--color-surface);
    border-radius: var(--radius-md);
    border: 1px solid var(--color-border);
    overflow: hidden;
    transition: all var(--transition);
    box-shadow: 0 2px 8px var(--color-shadow);
}

details:hover {
    border-color: var(--color-accent);
    box-shadow: 0 4px 16px var(--color-shadow);
}

summary {
    padding: 1.25rem 1.5rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: space-between;
    list-style: none;
    transition: background var(--transition);
}

summary::-webkit-details-marker {
    display: none;
}

summary::after {
    content: '+';
    font-size: 1.4rem;
    font-weight: 300;
    color: var(--color-accent);
    transition: transform var(--transition);
}

details[open] summary::after {
    transform: rotate(45deg);
}

details[open] summary {
    background: var(--color-accent-soft);
}

details p {
    padding: 0 1.5rem 1.25rem;
    margin: 0;
}

/* ===== HowTo ===== */
.howto-steps {
    max-width: 720px;
    margin: 0 auto;
    background: var(--color-surface);
    border-radius: var(--radius-lg);
    padding: 2rem 2.5rem;
    box-shadow: 0 4px 20px var(--color-shadow);
    border: 1px solid var(--color-border);
}

.howto-steps ol {
    list-style: decimal;
    padding-left: 1.5rem;
    margin-bottom: 1.5rem;
}

.howto-steps li {
    margin-bottom: 1rem;
    line-height: 1.7;
    color: var(--color-text-secondary);
}

.howto-steps li strong {
    color: var(--color-text);
}

.howto-steps p {
    font-weight: 500;
    color: var(--color-accent);
    margin: 0;
}

/* ===== Contact ===== */
address {
    font-style: normal;
    background: var(--color-surface);
    border-radius: var(--radius-lg);
    padding: 2.5rem;
    max-width: 600px;
    margin: 0 auto;
    box-shadow: 0 4px 20px var(--color-shadow);
    border: 1px solid var(--color-border);
    text-align: center;
}

address p {
    margin-bottom: 0.75rem;
    font-size: 1.05rem;
}

address a {
    font-weight: 600;
}

/* ===== Footer ===== */
footer {
    background: var(--color-primary);
    color: rgba(255,255,255,0.8);
    padding: 2.5rem 1.5rem;
}

.footer-content {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    align-items: center;
    gap: 1rem;
}

.footer-content p {
    color: rgba(255,255,255,0.7);
    margin: 0;
}

.footer-links {
    display: flex;
    gap: 1.5rem;
}

.footer-links a {
    color: rgba(255,255,255,0.7);
    font-size: 0.9rem;
    transition: color var(--transition);
}

.footer-links a:hover {
    color: #ffffff;
}

/* ===== Back to Top ===== */
.back-to-top {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: var(--color-accent);
    color: #ffffff;
    border: none;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 4px 16px rgba(230, 57, 70, 0.35);
    opacity: 0;
    visibility: hidden;
    transform: translateY(20px);
    transition: all var(--transition);
    z-index: 999;
}

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

.back-to-top:hover {
    background: var(--color-accent-hover);
    transform: translateY(-4px);
    box-shadow: 0 8px 24px rgba(230, 57, 70, 0.45);
}

/* ===== 滚动动画 (Intersection Observer 模拟) ===== */
/* CSS 仅做初始隐藏，JS 控制可见性，此处用 @keyframes 提供入场效果 */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(40px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

section {
    animation: fadeInUp 0.6s ease forwards;
}

/* 后续 section 延迟 */
section:nth-child(2) { animation-delay: 0.1s; }
section:nth-child(3) { animation-delay: 0.15s; }
section:nth-child(4) { animation-delay: 0.2s; }
section:nth-child(5) { animation-delay: 0.25s; }
section:nth-child(6) { animation-delay: 0.3s; }
section:nth-child(7) { animation-delay: 0.35s; }
section:nth-child(8) { animation-delay: 0.4s; }
section:nth-child(9) { animation-delay: 0.45s; }
section:nth-child(10) { animation-delay: 0.5s; }
section:nth-child(11) { animation-delay: 0.55s; }

/* 卡片等子元素也添加微动 */
.card, .about-grid article, blockquote, details, .feature-list li, address, .howto-steps {
    transition: all var(--transition);
}

/* ===== 响应式设计 ===== */
@media (max-width: 768px) {
    .nav-links {
        position: fixed;
        top: var(--nav-height);
        left: 0;
        width: 100%;
        background: var(--color-surface-glass);
        backdrop-filter: blur(20px);
        -webkit-backdrop-filter: blur(20px);
        flex-direction: column;
        padding: 1rem 1.5rem;
        gap: 0.25rem;
        border-bottom: 1px solid var(--color-border);
        transform: translateY(-120%);
        opacity: 0;
        transition: all 0.35s ease;
        box-shadow: 0 8px 32px var(--color-shadow);
    }

    .nav-links.active {
        transform: translateY(0);
        opacity: 1;
    }

    .nav-links li a {
        width: 100%;
        padding: 0.75rem 1rem;
        font-size: 1.05rem;
    }

    .mobile-menu-toggle {
        display: flex;
    }

    .hero {
        padding-top: calc(var(--nav-height) + 1.5rem);
        padding-bottom: 3rem;
    }

    .hero-content h1 {
        font-size: clamp(1.8rem, 7vw, 2.6rem);
    }

    .hero-actions {
        flex-direction: column;
        align-items: center;
    }

    .btn {
        width: 100%;
        max-width: 280px;
    }

    main > section {
        padding: 3rem 1rem;
    }

    .about-grid,
    .card-grid,
    .testimonial-grid,
    .feature-list {
        grid-template-columns: 1fr;
    }

    .howto-steps {
        padding: 1.5rem;
    }

    .footer-content {
        flex-direction: column;
        text-align: center;
    }

    .footer-links {
        justify-content: center;
        flex-wrap: wrap;
    }

    .back-to-top {
        bottom: 1.5rem;
        right: 1.5rem;
        width: 44px;
        height: 44px;
    }
}

@media (max-width: 480px) {
    .nav-container {
        padding-left: 1rem;
        padding-right: 1rem;
    }

    .hero-content p {
        font-size: 1rem;
    }

    .card {
        padding: 1.5rem 1rem;
    }

    blockquote {
        padding: 1.5rem;
    }

    address {
        padding: 1.5rem;
    }
}

/* 大屏优化 */
@media (min-width: 1400px) {
    .hero {
        padding-left: 2rem;
        padding-right: 2rem;
    }

    .card-grid {
        grid-template-columns: repeat(4, 1fr);
    }
}

/* 打印样式 */
@media print {
    header, .back-to-top, .dark-mode-toggle, .mobile-menu-toggle {
        display: none;
    }

    body {
        background: #fff;
        color: #000;
    }

    section {
        page-break-inside: avoid;
    }
}