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

:root {
    --primary: #1a73e8;
    --primary-dark: #1557b0;
    --primary-light: #e8f0fe;
    --secondary: #00a884;
    --accent: #e8870a;
    --accent-red: #d93025;
    --text-primary: #202124;
    --text-secondary: #5f6368;
    --text-light: #80868b;
    --bg-white: #ffffff;
    --bg-light: #f8f9fa;
    --bg-gray: #f1f3f4;
    --border-color: #dadce0;
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
    --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
    --shadow-lg: 0 8px 30px rgba(0,0,0,0.12);
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    --max-width: 1200px;
    --header-height: 70px;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
    color: var(--text-primary);
    background: var(--bg-white);
    line-height: 1.6;
    min-width: 320px;
}

.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 20px;
}

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

ul {
    list-style: none;
}

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

/* ========================================
   Header / 导航栏
   ======================================== */
.header {
    position: sticky;
    top: 0;
    z-index: 1000;
    background: var(--bg-white);
    box-shadow: var(--shadow-sm);
    height: var(--header-height);
    transition: var(--transition);
}

.header.scrolled {
    box-shadow: var(--shadow-md);
}

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

/* Logo */
.logo a {
    display: flex;
    align-items: center;
}

.logo a img {
    display: block;
    transition: var(--transition);
}

.logo:hover a img {
    transform: scale(1.05);
}

/* Navigation */
.nav-list {
    display: flex;
    align-items: center;
    gap: 4px;
}

.nav-link {
    display: block;
    padding: 10px 18px;
    font-size: 15px;
    font-weight: 500;
    color: var(--text-primary);
    border-radius: var(--radius-sm);
    transition: var(--transition);
    position: relative;
}

.nav-link:hover,
.nav-link.active {
    color: var(--primary);
    background: var(--primary-light);
}

/* Dropdown */
.nav-dropdown {
    position: relative;
}

.nav-dropdown .nav-link {
    display: flex;
    align-items: center;
    gap: 4px;
}

.dropdown-arrow {
    font-size: 10px;
    transition: transform 0.3s;
}

.nav-dropdown:hover .dropdown-arrow {
    transform: rotate(180deg);
}

.dropdown-menu {
    position: absolute;
    top: 100%;
    left: 0;
    min-width: 220px;
    background: var(--bg-white);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    padding: 8px 0;
    opacity: 0;
    visibility: hidden;
    transform: translateY(8px);
    transition: var(--transition);
}

.nav-dropdown:hover .dropdown-menu {
    opacity: 1;
    visibility: visible;
    transform: translateY(4px);
}

.dropdown-menu a {
    display: block;
    padding: 10px 20px;
    font-size: 14px;
    color: var(--text-primary);
    transition: var(--transition);
}

.dropdown-menu a:hover,
.dropdown-menu a.active {
    color: var(--primary);
    background: var(--primary-light);
}

/* Mobile Menu Toggle */
.mobile-menu-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
    z-index: 1001;
}

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

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

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

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

/* ========================================
   Shared Section Title / 共享标题
   ======================================== */
.section-title {
    font-size: 30px;
    font-weight: 700;
    color: var(--text-primary);
    text-align: center;
    margin-bottom: 16px;
}

.section-subtitle {
    font-size: 16px;
    color: var(--text-secondary);
    text-align: center;
    margin-bottom: 48px;
}

/* ========================================
   Breadcrumb / 面包屑
   ======================================== */
.breadcrumb-section {
    background: var(--bg-light);
    border-bottom: 1px solid var(--border-color);
    padding: 12px 0;
}

.breadcrumb {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 13px;
    color: var(--text-light);
}

.breadcrumb a {
    color: var(--text-secondary);
    transition: var(--transition);
}

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

.breadcrumb .separator {
    color: var(--border-color);
}

.breadcrumb .current {
    color: var(--text-primary);
    font-weight: 500;
}

/* ========================================
   Footer / 底部
   ======================================== */
.footer {
    background: #1a1f36;
    color: #b0b8c8;
    padding: 60px 0 0;
}

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

.footer-col h3 {
    color: #fff;
    font-size: 18px;
    font-weight: 600;
    margin-bottom: 20px;
    position: relative;
    padding-bottom: 12px;
}

.footer-col h3::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 40px;
    height: 3px;
    background: var(--primary);
    border-radius: 2px;
}

.contact-list li {
    display: flex;
    align-items: flex-start;
    gap: 10px;
    margin-bottom: 12px;
    font-size: 14px;
    line-height: 1.6;
}

.contact-icon {
    flex-shrink: 0;
    font-size: 16px;
    width: 20px;
    text-align: center;
}

.footer-about p {
    font-size: 14px;
    line-height: 1.8;
    margin-bottom: 12px;
}

/* Footer Bottom */
.footer-bottom {
    border-top: 1px solid rgba(255,255,255,0.08);
    padding: 20px 0;
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 13px;
}

.footer-tech {
    color: rgba(255,255,255,0.3);
}

/* ========================================
   Back to Top / 返回顶部
   ======================================== */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 44px;
    height: 44px;
    background: var(--primary);
    color: #fff;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    visibility: hidden;
    transform: translateY(10px);
    transition: var(--transition);
    z-index: 999;
    box-shadow: var(--shadow-md);
}

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

.back-to-top:hover {
    background: var(--primary-dark);
    transform: translateY(-3px);
    box-shadow: var(--shadow-lg);
}

/* ========================================
   Animations / 动画
   ======================================== */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.product-card {
    animation: fadeInUp 0.5s ease forwards;
}

.product-card:nth-child(1) { animation-delay: 0.1s; }
.product-card:nth-child(2) { animation-delay: 0.2s; }
.product-card:nth-child(3) { animation-delay: 0.3s; }
.product-card:nth-child(4) { animation-delay: 0.4s; }

/* ========================================
   Responsive / 响应式
   ======================================== */

/* Tablet */
@media (max-width: 992px) {
    :root {
        --header-height: 60px;
    }

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

}

/* Mobile */
@media (max-width: 768px) {
    /* --- Header / 导航 --- */
    :root {
        --header-height: 56px;
    }

    .header {
        height: 56px;
    }

    .header-inner {
        height: 56px;
    }

    .logo a img {
        height: 30px;
        width: auto;
    }

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

    .nav {
        position: fixed;
        top: 0;
        right: -100%;
        width: 280px;
        height: 100vh;
        background: var(--bg-white);
        box-shadow: -4px 0 20px rgba(0,0,0,0.15);
        padding: 72px 20px 24px;
        transition: right 0.35s cubic-bezier(0.4, 0, 0.2, 1);
        z-index: 999;
        overflow-y: auto;
    }

    .nav.active {
        right: 0;
    }

    .nav-list {
        flex-direction: column;
        gap: 2px;
    }

    .nav-link {
        padding: 14px 16px;
        font-size: 15px;
        border-radius: 8px;
    }

    .dropdown-menu {
        position: static;
        box-shadow: none;
        opacity: 1;
        visibility: visible;
        transform: none;
        padding: 0 0 0 16px;
        min-width: auto;
        display: none;
        background: var(--bg-light);
        border-radius: 8px;
        margin: 4px 0;
    }

    .nav-dropdown.open .dropdown-menu {
        display: block;
    }

    .dropdown-menu a {
        padding: 12px 16px;
        font-size: 14px;
    }


    /* --- Footer --- */
    .footer {
        padding: 40px 0 0;
    }

    .footer-grid {
        grid-template-columns: 1fr;
        gap: 28px;
        margin-bottom: 28px;
    }

    .footer-col h3 {
        font-size: 16px;
        margin-bottom: 14px;
    }

    .contact-list li {
        font-size: 13px;
    }

    .footer-about p {
        font-size: 13px;
    }

    .footer-bottom {
        flex-direction: column;
        gap: 6px;
        text-align: center;
        font-size: 12px;
        padding: 16px 0;
    }

    /* --- Breadcrumb --- */
    .breadcrumb {
        font-size: 12px;
    }

    /* --- Back to Top --- */
    .back-to-top {
        bottom: 80px;
        right: 16px;
        width: 40px;
        height: 40px;
    }

    /* --- General Spacing --- */
    .container {
        padding: 0 16px;
    }
}

/* Small Mobile */
@media (max-width: 480px) {
    .container {
        padding: 0 12px;
    }

    /* --- Footer --- */
    .footer {
        padding: 32px 0 0;
    }

    .footer-grid {
        gap: 22px;
    }

    .back-to-top {
        bottom: 72px;
        right: 12px;
        width: 36px;
        height: 36px;
    }

}