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

:root {
    --primary: #1a56db;
    --primary-dark: #0f3a9e;
    --primary-light: #e8effc;
    --dark: #1a1a2e;
    --text: #333;
    --text-light: #666;
    --text-lighter: #999;
    --white: #fff;
    --bg-light: #f7f8fa;
    --bg-section: #f0f2f5;
    --border: #e5e7eb;
    --shadow: 0 4px 24px rgba(0,0,0,.08);
    --shadow-hover: 0 8px 32px rgba(0,0,0,.12);
    --radius: 8px;
    --transition: .3s ease;
    --container: 1200px;
}

html { scroll-behavior: smooth; font-size: 16px; }
body { font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei", "Helvetica Neue", sans-serif; color: var(--text); line-height: 1.6; background: var(--white); overflow-x: hidden; }
a { text-decoration: none; color: inherit; transition: var(--transition); }
img { max-width: 100%; height: auto; display: block; }
ul { list-style: none; }

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

/* ===== Buttons ===== */
.btn { display: inline-block; padding: 12px 32px; border-radius: 4px; font-size: 15px; font-weight: 500; letter-spacing: .5px; transition: var(--transition); cursor: pointer; border: 2px solid transparent; }
.btn-primary { background: var(--primary); color: var(--white); border-color: var(--primary); }
.btn-primary:hover { background: var(--primary-dark); border-color: var(--primary-dark); transform: translateY(-2px); }
.btn-outline { background: transparent; color: var(--primary); border-color: var(--primary); }
.btn-outline:hover { background: var(--primary); color: var(--white); transform: translateY(-2px); }
.btn-white { background: var(--white); color: var(--primary); border-color: var(--white); }
.btn-white:hover { background: var(--primary-light); transform: translateY(-2px); }

/* ===== Header ===== */
.header { position: fixed; top: 0; left: 0; right: 0; z-index: 1000; background: rgba(255,255,255,.95); backdrop-filter: blur(10px); border-bottom: 1px solid rgba(0,0,0,.06); transition: var(--transition); }
.header.scrolled { box-shadow: 0 2px 20px rgba(0,0,0,.08); }
.header-inner { display: flex; align-items: center; justify-content: space-between; height: 72px; }
.logo { display: flex; align-items: center; gap: 10px; }
.logo-text { font-size: 22px; font-weight: 700; color: var(--primary); letter-spacing: 1px; }
.nav { display: flex; gap: 6px; }
.nav-link { padding: 8px 16px; font-size: 15px; color: var(--text); border-radius: 4px; font-weight: 500; }
.nav-link:hover, .nav-link.active { color: var(--primary); background: var(--primary-light); }
.header-actions { display: flex; align-items: center; gap: 16px; }
.header-phone { font-size: 14px; font-weight: 600; color: var(--primary); display: flex; align-items: center; gap: 6px; }
.mobile-menu-btn { display: none; width: 28px; height: 20px; background: none; border: none; cursor: pointer; position: relative; }
.mobile-menu-btn span { display: block; width: 100%; height: 2px; background: var(--text); position: absolute; left: 0; transition: var(--transition); }
.mobile-menu-btn span:nth-child(1) { top: 0; }
.mobile-menu-btn span:nth-child(2) { top: 9px; }
.mobile-menu-btn span:nth-child(3) { top: 18px; }
.mobile-menu-btn.active span:nth-child(1) { top: 9px; transform: rotate(45deg); }
.mobile-menu-btn.active span:nth-child(2) { opacity: 0; }
.mobile-menu-btn.active span:nth-child(3) { top: 9px; transform: rotate(-45deg); }

/* ===== Hero ===== */
.hero { position: relative; height: 600px; overflow: hidden; margin-top: 72px; }
.hero-slide { position: absolute; inset: 0; opacity: 0; transition: opacity .8s ease; }
.hero-slide.active { opacity: 1; }
.hero-bg { position: absolute; inset: 0; background-size: cover; background-position: center; }
.hero-bg::after { content: ''; position: absolute; inset: 0; background: linear-gradient(135deg, rgba(10,20,40,.75) 0%, rgba(10,20,40,.3) 100%); }
.hero-content { position: relative; z-index: 2; height: 100%; display: flex; flex-direction: column; justify-content: center; max-width: 680px; }
.hero-tag { display: inline-block; padding: 6px 16px; background: rgba(255,255,255,.15); backdrop-filter: blur(4px); border: 1px solid rgba(255,255,255,.2); border-radius: 20px; color: var(--white); font-size: 14px; margin-bottom: 20px; width: fit-content; }
.hero-content h1 { font-size: 48px; font-weight: 700; color: var(--white); line-height: 1.2; margin-bottom: 16px; }
.hero-content p { font-size: 18px; color: rgba(255,255,255,.85); margin-bottom: 32px; line-height: 1.7; }
.hero-dots { position: absolute; bottom: 30px; left: 50%; transform: translateX(-50%); z-index: 10; display: flex; gap: 10px; }
.hero-dot { width: 12px; height: 12px; border-radius: 50%; border: 2px solid rgba(255,255,255,.6); background: transparent; cursor: pointer; transition: var(--transition); padding: 0; }
.hero-dot.active { background: var(--white); border-color: var(--white); }

/* ===== Stats Bar ===== */
.stats-bar { background: var(--primary); padding: 40px 0; }
.stats-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 20px; text-align: center; }
.stat-item { color: var(--white); }
.stat-number { font-size: 42px; font-weight: 700; }
.stat-suffix { font-size: 24px; font-weight: 600; color: rgba(255,255,255,.8); }
.stat-label { display: block; font-size: 14px; color: rgba(255,255,255,.7); margin-top: 4px; }

/* ===== Sections Common ===== */
.section { padding: 80px 0; }
.section-header { text-align: center; margin-bottom: 50px; }
.section-header-light .section-title { color: var(--white); }
.section-header-light .section-subtitle { color: rgba(255,255,255,.7); }
.section-tag { display: inline-block; padding: 4px 14px; background: var(--primary-light); color: var(--primary); border-radius: 20px; font-size: 13px; font-weight: 600; margin-bottom: 16px; }
.section-title { font-size: 32px; font-weight: 700; color: var(--dark); margin-bottom: 12px; }
.section-subtitle { font-size: 16px; color: var(--text-light); }
.section-action { text-align: center; margin-top: 40px; }

/* ===== Product Categories ===== */
.products-section { background: var(--bg-light); }
.product-categories { display: grid; grid-template-columns: repeat(4, 1fr); gap: 24px; }
.product-card { background: var(--white); border-radius: var(--radius); overflow: hidden; box-shadow: var(--shadow); transition: var(--transition); display: flex; flex-direction: column; }
.product-card:hover { transform: translateY(-6px); box-shadow: var(--shadow-hover); }
.product-card-img { height: 220px; overflow: hidden; background: #f5f5f5; }
.product-card-img img { width: 100%; height: 100%; object-fit: cover; transition: transform .5s ease; }
.product-card:hover .product-card-img img { transform: scale(1.05); }
.product-card-info { padding: 24px; flex: 1; display: flex; flex-direction: column; }
.product-card-info h3 { font-size: 18px; font-weight: 600; color: var(--dark); margin-bottom: 8px; }
.product-card-info p { font-size: 14px; color: var(--text-light); flex: 1; }
.card-arrow { display: inline-flex; align-items: center; justify-content: center; width: 36px; height: 36px; border-radius: 50%; background: var(--primary-light); color: var(--primary); margin-top: 16px; transition: var(--transition); }
.product-card:hover .card-arrow { background: var(--primary); color: var(--white); }

/* ===== Advantages ===== */
.advantages-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 24px; }
.advantage-item { text-align: center; padding: 40px 24px; background: var(--white); border-radius: var(--radius); border: 1px solid var(--border); transition: var(--transition); }
.advantage-item:hover { border-color: var(--primary); box-shadow: var(--shadow); transform: translateY(-4px); }
.advantage-icon { width: 64px; height: 64px; margin: 0 auto 20px; display: flex; align-items: center; justify-content: center; background: var(--primary-light); border-radius: 50%; font-size: 28px; color: var(--primary); transition: var(--transition); }
.advantage-item:hover .advantage-icon { background: var(--primary); color: var(--white); }
.advantage-item h3 { font-size: 18px; font-weight: 600; margin-bottom: 12px; color: var(--dark); }
.advantage-item p { font-size: 14px; color: var(--text-light); line-height: 1.7; }

/* ===== About Preview ===== */
.about-preview { background: var(--bg-light); }
.about-preview-inner { display: grid; grid-template-columns: 1fr 1fr; gap: 60px; align-items: center; }
.about-preview-text h2 { font-size: 28px; font-weight: 700; color: var(--dark); margin-bottom: 20px; line-height: 1.4; }
.about-preview-text p { font-size: 15px; color: var(--text-light); margin-bottom: 16px; line-height: 1.8; }
.about-preview-text .btn { margin-top: 12px; }
.about-preview-img { border-radius: var(--radius); overflow: hidden; box-shadow: var(--shadow); }
.about-preview-img img { width: 100%; }

/* ===== Solutions ===== */
.solutions-section { background: var(--dark); }
.solutions-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 20px; }
.solution-card { position: relative; border-radius: var(--radius); overflow: hidden; height: 320px; cursor: pointer; }
.solution-card img { width: 100%; height: 100%; object-fit: cover; transition: transform .5s ease; }
.solution-card:hover img { transform: scale(1.08); }
.solution-card-overlay { position: absolute; inset: 0; background: linear-gradient(to top, rgba(0,0,0,.8) 0%, rgba(0,0,0,.1) 60%); z-index: 1; transition: var(--transition); }
.solution-card:hover .solution-card-overlay { background: linear-gradient(to top, rgba(26,86,219,.85) 0%, rgba(26,86,219,.2) 60%); }
.solution-card-content { position: absolute; bottom: 0; left: 0; right: 0; padding: 24px; z-index: 2; }
.solution-card-content h3 { font-size: 18px; font-weight: 600; color: var(--white); margin-bottom: 6px; }
.solution-card-content p { font-size: 13px; color: rgba(255,255,255,.8); }

/* ===== News ===== */
.news-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.news-card { background: var(--white); border-radius: var(--radius); overflow: hidden; box-shadow: var(--shadow); transition: var(--transition); display: flex; flex-direction: column; }
.news-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-hover); }
.news-card-img { height: 200px; overflow: hidden; }
.news-card-img img { width: 100%; height: 100%; object-fit: cover; transition: transform .5s ease; }
.news-card:hover .news-card-img img { transform: scale(1.05); }
.news-card-body { padding: 24px; flex: 1; display: flex; flex-direction: column; }
.news-tag { display: inline-block; padding: 3px 10px; background: var(--primary-light); color: var(--primary); border-radius: 3px; font-size: 12px; font-weight: 600; margin-bottom: 12px; width: fit-content; }
.news-card-body h3 { font-size: 16px; font-weight: 600; color: var(--dark); margin-bottom: 10px; line-height: 1.5; display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; }
.news-card-body p { font-size: 14px; color: var(--text-light); line-height: 1.6; flex: 1; display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; }
.news-date { font-size: 13px; color: var(--text-lighter); margin-top: 16px; }

/* ===== CTA ===== */
.cta-section { position: relative; padding: 80px 0; background: url('https://www.saejong.cn/upload/image/2025/04/07/bc9faf6a-fa22-4197-9a3a-b64c013a1b5e.jpg') center/cover no-repeat; }
.cta-section::before { content: ''; position: absolute; inset: 0; background: rgba(10,20,40,.7); }
.cta-inner { position: relative; z-index: 1; display: flex; align-items: center; justify-content: space-between; }
.cta-text h2 { font-size: 28px; font-weight: 700; color: #fff; margin-bottom: 8px; }
.cta-text p { font-size: 16px; color: rgba(255,255,255,.8); }

/* ===== Footer ===== */
.footer { background: var(--dark); color: rgba(255,255,255,.7); padding: 60px 0 0; }
.footer-grid { display: grid; grid-template-columns: 1.5fr 1fr 1fr 1.5fr; gap: 40px; padding-bottom: 40px; border-bottom: 1px solid rgba(255,255,255,.1); }
.footer-logo { font-size: 20px; font-weight: 700; color: var(--white); margin-bottom: 16px; }
.footer-about p { font-size: 14px; line-height: 1.8; }
.footer-social { display: flex; gap: 12px; margin-top: 16px; }
.footer-social a { width: 36px; height: 36px; border-radius: 50%; background: rgba(255,255,255,.1); display: flex; align-items: center; justify-content: center; color: var(--white); font-size: 16px; transition: var(--transition); }
.footer-social a:hover { background: var(--primary); }
.footer-col h4 { font-size: 16px; font-weight: 600; color: var(--white); margin-bottom: 20px; }
.footer-col ul li { margin-bottom: 10px; }
.footer-col ul li a, .footer-contact ul li { font-size: 14px; display: flex; align-items: flex-start; gap: 8px; }
.footer-col ul li a:hover { color: var(--white); }
.footer-contact ul li i { margin-top: 4px; color: var(--primary); }
.footer-bottom { padding: 20px 0; text-align: center; font-size: 13px; color: rgba(255,255,255,.4); }

/* ===== Back to Top ===== */
.back-to-top { position: fixed; bottom: 30px; right: 30px; width: 44px; height: 44px; border-radius: 50%; background: var(--primary); color: var(--white); border: none; cursor: pointer; font-size: 18px; display: flex; align-items: center; justify-content: center; opacity: 0; visibility: hidden; transition: var(--transition); z-index: 999; box-shadow: 0 4px 12px rgba(26,86,219,.3); }
.back-to-top.visible { opacity: 1; visibility: visible; }
.back-to-top:hover { transform: translateY(-3px); }

/* ===== Animations ===== */
.fade-in { opacity: 0; transform: translateY(30px); transition: opacity .6s ease, transform .6s ease; }
.fade-in.visible { opacity: 1; transform: translateY(0); }

/* ===== Responsive ===== */
@media (max-width: 1024px) {
    .product-categories, .advantages-grid, .solutions-grid { grid-template-columns: repeat(2, 1fr); }
    .about-preview-inner { grid-template-columns: 1fr; gap: 40px; }
    .hero-content h1 { font-size: 36px; }
    .stats-grid { grid-template-columns: repeat(2, 1fr); gap: 30px; }
    .footer-grid { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 768px) {
    .nav { position: fixed; top: 72px; left: 0; right: 0; background: var(--white); flex-direction: column; padding: 20px; gap: 4px; box-shadow: 0 4px 20px rgba(0,0,0,.1); transform: translateY(-120%); transition: var(--transition); z-index: 999; }
    .nav.open { transform: translateY(0); }
    .mobile-menu-btn { display: block; }
    .header-phone { display: none; }
    .hero { height: 480px; }
    .hero-content h1 { font-size: 28px; }
    .hero-content p { font-size: 15px; }
    .section { padding: 50px 0; }
    .section-title { font-size: 24px; }
    .product-categories, .advantages-grid, .news-grid { grid-template-columns: 1fr; }
    .solutions-grid { grid-template-columns: repeat(2, 1fr); }
    .solution-card { height: 240px; }
    .stats-grid { grid-template-columns: repeat(2, 1fr); }
    .stat-number { font-size: 32px; }
    .cta-inner { flex-direction: column; text-align: center; gap: 20px; }
    .footer-grid { grid-template-columns: 1fr; gap: 30px; }
}

@media (max-width: 480px) {
    .hero { height: 400px; }
    .hero-content h1 { font-size: 24px; }
    .solutions-grid { grid-template-columns: 1fr; }
    .btn { padding: 10px 24px; font-size: 14px; }
}