:root {
  --primary: #0a5c8a;
  --primary-dark: #083d5c;
  --accent: #00b4d8;
  --accent-light: #90e0ef;
  --bg-light: #f0f7fa;
  --text: #2c3e50;
  --text-light: #6c757d;
  --white: #ffffff;
  --shadow: 0 4px 20px rgba(10,92,138,0.1);
  --shadow-hover: 0 8px 32px rgba(10,92,138,0.18);
  --radius: 12px;
}

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

html { scroll-behavior: smooth; scroll-padding-top: 72px; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  color: var(--text);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  background: var(--bg-light);
}

/* NAVBAR (same as index) */
.navbar {
  background: rgba(255,255,255,0.97);
  backdrop-filter: blur(10px);
  box-shadow: 0 1px 12px rgba(0,0,0,0.06);
  padding: 0;
  min-height: 72px;
  transition: box-shadow 0.3s;
  align-items: center !important;
}
.navbar-brand {
  display: flex;
  align-items: center;
  padding: 0 !important;
}
.navbar.scrolled { box-shadow: 0 2px 20px rgba(0,0,0,0.1); }
.navbar-brand img { height: 42px; width: auto; }
.nav-link {
  color: var(--text) !important;
  font-weight: 500;
  padding: 22px 20px !important;
  position: relative;
  transition: color 0.25s;
  font-size: 15px;
}
.nav-link:hover, .nav-link.active { color: var(--accent) !important; }
.nav-link::after {
  content: '';
  position: absolute;
  bottom: 12px;
  left: 20px; right: 20px;
  height: 2px;
  background: var(--accent);
  transform: scaleX(0);
  transition: transform 0.3s;
}
.nav-link:hover::after, .nav-link.active::after { transform: scaleX(1); }

/* PRODUCT DETAIL */
.product-hero {
  background: linear-gradient(135deg, #0a5c8a 0%, #083d5c 100%);
  padding: 100px 0 40px;
  text-align: center;
  color: #fff;
}
.product-hero h1 {
  font-size: clamp(22px, 4vw, 36px);
  font-weight: 700;
  margin-bottom: 8px;
}
.product-hero .breadcrumb-custom {
  display: flex; justify-content: center; gap: 8px;
  font-size: 14px;
  opacity: 0.8;
  margin-top: 12px;
}
.product-hero .breadcrumb-custom a {
  color: var(--accent-light); text-decoration: none;
}
.product-hero .breadcrumb-custom a:hover { text-decoration: underline; }

.product-img-card {
  background: var(--white);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  overflow: hidden;
  max-width: 800px;
  margin: -20px auto 0;
  position: relative;
  z-index: 2;
  padding: 20px;
}
.product-img-card img {
  width: 100%;
  height: auto;
  display: block;
  border-radius: 8px;
}

.product-info {
  max-width: 800px;
  margin: 30px auto 0;
}
.product-info-card {
  background: var(--white);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 32px;
}
.product-info-card h4 {
  font-size: 20px;
  color: var(--primary-dark);
  margin-bottom: 16px;
  padding-bottom: 12px;
  border-bottom: 2px solid var(--bg-light);
}
.product-info-card p {
  color: var(--text);
  font-size: 15px;
  line-height: 1.9;
}

/* NAV ARROWS */
.nav-arrows {
  display: flex;
  justify-content: space-between;
  align-items: center;
  max-width: 800px;
  margin: 30px auto 60px;
  gap: 16px;
}
.nav-arrow {
  display: flex; align-items: center; gap: 10px;
  padding: 12px 24px;
  border-radius: var(--radius);
  background: var(--white);
  box-shadow: var(--shadow);
  text-decoration: none;
  color: var(--primary);
  font-weight: 500;
  font-size: 14px;
  transition: transform 0.25s, box-shadow 0.25s;
  flex: 1;
}
.nav-arrow:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-hover);
  color: var(--accent);
}
.nav-arrow.next { text-align: right; justify-content: flex-end; }
.nav-arrow.disabled { opacity: 0.4; pointer-events: none; }
.nav-arrow i { font-size: 16px; color: var(--accent); }
.nav-arrow .arrow-label { font-size: 12px; color: var(--text-light); display: block; }
.nav-arrow .arrow-title { font-size: 14px; font-weight: 600; }

/* PRODUCT LIST LINK */
.all-products {
  text-align: center;
  margin-bottom: 60px;
}
.all-products a {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 10px 24px;
  border-radius: 30px;
  border: 2px solid var(--accent);
  color: var(--accent);
  text-decoration: none;
  font-weight: 500;
  font-size: 14px;
  transition: background 0.25s, color 0.25s;
}
.all-products a:hover {
  background: var(--accent);
  color: #fff;
}

/* FOOTER */
.footer {
  background: var(--primary-dark);
  color: rgba(255,255,255,0.7);
  padding: 28px 0;
  text-align: center;
  font-size: 13px;
}
.footer a { color: var(--accent-light); text-decoration: none; }
.footer a:hover { text-decoration: underline; }

/* BACK TO TOP */
.back-top {
  position: fixed; bottom: 32px; right: 32px;
  width: 44px; height: 44px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--primary), var(--accent));
  color: #fff; border: none;
  box-shadow: 0 4px 16px rgba(0,180,216,0.3);
  display: flex; align-items: center; justify-content: center;
  font-size: 18px; cursor: pointer;
  opacity: 0; visibility: hidden;
  transform: translateY(10px);
  transition: opacity 0.3s, transform 0.3s;
  z-index: 999;
}
.back-top.show { opacity: 1; visibility: visible; transform: translateY(0); }
.back-top:hover { transform: translateY(-2px); }

/* FADE */
.fade-up {
  opacity: 0; transform: translateY(30px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}
.fade-up.visible { opacity: 1; transform: translateY(0); }

/* RESPONSIVE */
@media (max-width: 991.98px) {
  .navbar { align-items: flex-start !important; }
  .navbar-brand, .navbar-toggler { margin-top: 15px !important; }
  .navbar-collapse {
    background: rgba(255,255,255,0.98);
    backdrop-filter: blur(10px);
    border-radius: 0 0 var(--radius) var(--radius);
    box-shadow: 0 8px 24px rgba(0,0,0,0.08);
    padding: 8px 16px;
    margin-top: 4px;
  }
  .navbar-nav .nav-link { padding: 12px 8px !important; font-size: 15px; }
  .nav-link::after { display: none; }
}

@media (max-width: 768px) {
  .product-hero { padding: 90px 0 30px; }
  .product-img-card { margin: -10px 16px 0; padding: 12px; }
  .product-info-card { padding: 20px; }
  .nav-arrows { flex-direction: column; margin-bottom: 40px; }
  .nav-arrow { width: 100%; }
  .back-top { bottom: 20px; right: 20px; width: 40px; height: 40px; }
  .nav-link { padding: 18px 12px !important; font-size: 14px; }
}