/* ========================================
   苏州圣旺鑫电子科技有限公司官网
   样式表 — 工业简约科技风
   ======================================== */

/* --- CSS Custom Properties --- */
:root {
  --color-primary: #1a3a4a;
  --color-accent: #2563eb;
  --color-copper: #c79148;
  --color-bg: #ffffff;
  --color-bg-alt: #f5f6f8;
  --color-text: #1f2937;
  --color-text-light: #6b7280;
  --color-border: #e5e7eb;
  --font-stack: -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei", sans-serif;
  --radius: 8px;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 30px rgba(0, 0, 0, 0.15);
  --max-width: 1200px;
  --nav-height: 70px;
}

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

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

body {
  font-family: var(--font-stack);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

a { text-decoration: none; color: inherit; }
ul { list-style: none; }
img { max-width: 100%; display: block; }
button { cursor: pointer; font: inherit; border: none; background: none; }

/* --- Utility --- */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

.section {
  padding: 100px 0;
}

.section--white { background: var(--color-bg); }
.section--gray  {
  background: var(--color-bg-alt);
  position: relative;
}
/* PCB 网格底纹 */
.section--gray::before {
  content: '';
  position: absolute;
  inset: 0;
  pointer-events: none;
  opacity: 0.25;
  background-image:
    linear-gradient(rgba(199,145,72,0.15) 1px, transparent 1px),
    linear-gradient(90deg, rgba(199,145,72,0.15) 1px, transparent 1px);
  background-size: 40px 40px;
}

.section__title {
  font-size: 2rem;
  font-weight: 700;
  color: var(--color-primary);
  text-align: center;
  margin-bottom: 12px;
}

/* PCB-trace 风格分割线：铜走线 + 过孔焊盘 */
.section__divider {
  width: 100px;
  height: 3px;
  background: var(--color-copper);
  margin: 0 auto 48px;
  position: relative;
  border-radius: 0;
}
.section__divider::before,
.section__divider::after {
  content: '';
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  width: 10px;
  height: 10px;
  background: var(--color-bg);
  border: 2px solid var(--color-copper);
  border-radius: 50%;
}
.section__divider::before { left: -5px; }
.section__divider::after { right: -5px; }
/* 中心过孔 */
.section__divider {
  background: linear-gradient(
    90deg,
    var(--color-copper) 0%,
    var(--color-copper) 40%,
    transparent 40%,
    transparent 44%,
    var(--color-copper) 44%,
    var(--color-copper) 56%,
    transparent 56%,
    transparent 60%,
    var(--color-copper) 60%,
    var(--color-copper) 100%
  );
}
.section--gray .section__divider::before,
.section--gray .section__divider::after {
  background: var(--color-bg-alt);
}

/* --- Buttons --- */
.btn {
  display: inline-block;
  padding: 12px 32px;
  border-radius: var(--radius);
  font-size: 1rem;
  font-weight: 600;
  transition: all 0.25s;
  text-align: center;
}

.btn--primary {
  background: var(--color-accent);
  color: #fff;
  position: relative;
}
/* 按钮上的铜色走线装饰 */
.btn--primary::after {
  content: '';
  position: absolute;
  bottom: 2px;
  left: 15%;
  right: 15%;
  height: 2px;
  background: rgba(199,145,72,0.4);
  border-radius: 1px;
}
.btn--primary:hover {
  background: #1d4ed8;
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}
.btn--primary:hover::after {
  background: var(--color-copper);
}

.btn--outline {
  border: 2px solid #fff;
  color: #fff;
}
.btn--outline:hover {
  background: #fff;
  color: var(--color-primary);
}

/* ========================================
   Navigation
   ======================================== */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  z-index: 1000;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(8px);
  transition: box-shadow 0.3s;
  height: var(--nav-height);
}

.nav--scrolled {
  box-shadow: 0 1px 6px rgba(0, 0, 0, 0.1);
}

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

.nav__logo {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-primary);
}

.nav__logo-img {
  height: 44px;
  width: auto;
  display: block;
  image-rendering: crisp-edges;
  mix-blend-mode: multiply;
  filter: contrast(1.05) saturate(1.1);
}

.nav__logo-icon {
  font-size: 1.5rem;
  color: var(--color-accent);
}

.nav__menu {
  display: flex;
  gap: 32px;
}

.nav__link {
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--color-text);
  position: relative;
  padding: 4px 0;
  transition: color 0.2s;
}

.nav__link::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--color-accent);
  transition: width 0.25s;
}
/* 导航小过孔点 */
.nav__link::before {
  content: '';
  position: absolute;
  top: 50%;
  left: -12px;
  transform: translateY(-50%);
  width: 5px;
  height: 5px;
  background: var(--color-copper);
  border-radius: 50%;
  opacity: 0;
  transition: opacity 0.25s;
}
.nav__link:hover::before,
.nav__link--active::before {
  opacity: 1;
}

.nav__link:hover,
.nav__link--active {
  color: var(--color-accent);
}

.nav__link:hover::after,
.nav__link--active::after {
  width: 100%;
}

/* Hamburger */
.nav__hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  padding: 4px;
}

.nav__hamburger span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--color-primary);
  transition: all 0.3s;
}

.nav__hamburger--open span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}
.nav__hamburger--open span:nth-child(2) {
  opacity: 0;
}
.nav__hamburger--open span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* ========================================
   Hero
   ======================================== */
.hero {
  position: relative;
  height: 100vh;
  min-height: 600px;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  overflow: hidden;
  background: linear-gradient(135deg, #0f2530 0%, var(--color-primary) 40%, #1a4456 100%);
}

/* PCB 走线 + 过孔 装饰背景 */
.hero__bg {
  position: absolute;
  inset: 0;
  opacity: 0.06;
  background-image:
    /* 45° 走线层 */
    linear-gradient(45deg, transparent 48%, rgba(255,255,255,0.8) 49%, transparent 51%),
    linear-gradient(-45deg, transparent 48%, rgba(255,255,255,0.8) 49%, transparent 51%),
    linear-gradient(135deg, transparent 48%, var(--color-copper) 49%, transparent 51%),
    linear-gradient(-135deg, transparent 48%, var(--color-copper) 49%, transparent 51%),
    /* 水平/垂直走线 */
    linear-gradient(90deg, transparent 48%, rgba(255,255,255,0.3) 49%, transparent 51%),
    linear-gradient(0deg, transparent 48%, rgba(255,255,255,0.3) 49%, transparent 51%);
  background-size: 80px 80px, 80px 80px, 80px 80px, 80px 80px, 160px 160px, 160px 160px;
  background-position: 0 0, 0 0, 0 0, 0 0, 40px 40px, 40px 40px;
}
/* 过孔装饰：散布的环形焊盘 */
.hero__bg::after {
  content: '';
  position: absolute;
  inset: 0;
  opacity: 0.5;
  background-image:
    radial-gradient(circle 4px, transparent 50%, var(--color-copper) 51%, transparent 53%),
    radial-gradient(circle 4px, transparent 50%, var(--color-copper) 51%, transparent 53%),
    radial-gradient(circle 4px, transparent 50%, var(--color-copper) 51%, transparent 53%),
    radial-gradient(circle 3px, transparent 50%, var(--color-copper) 51%, transparent 53%),
    radial-gradient(circle 3px, transparent 50%, var(--color-copper) 51%, transparent 53%),
    radial-gradient(circle 3px, transparent 50%, var(--color-copper) 51%, transparent 53%);
  background-size: 160px 160px, 160px 160px, 160px 160px, 120px 120px, 120px 120px, 120px 120px;
  background-position:
    40px 40px, 120px 80px, 80px 120px,
    60px 20px, 100px 100px, 20px 60px;
}

.hero__content {
  position: relative;
  z-index: 1;
}

.hero__title {
  font-size: 3rem;
  font-weight: 800;
  color: #fff;
  margin-bottom: 16px;
  letter-spacing: 2px;
}

.hero__subtitle {
  font-size: 1.2rem;
  color: rgba(255, 255, 255, 0.8);
  margin-bottom: 40px;
}

.hero__actions {
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
}

/* ========================================
   About
   ======================================== */
.about__grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 64px;
  align-items: center;
}

.about__text p {
  color: var(--color-text-light);
  margin-bottom: 16px;
  font-size: 1rem;
}

.about__stats {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
}

.stat-card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 32px 20px;
  text-align: center;
  transition: transform 0.25s, box-shadow 0.25s;
  position: relative;
  overflow: hidden;
}
/* PCB 测试点角标 */
.stat-card::before {
  content: '';
  position: absolute;
  top: 8px;
  right: 8px;
  width: 14px;
  height: 14px;
  background: var(--color-bg);
  border: 2px solid var(--color-copper);
  border-radius: 50%;
  opacity: 0.6;
  transition: opacity 0.25s, border-color 0.25s;
}
.stat-card::after {
  content: '';
  position: absolute;
  top: 12px;
  right: 12px;
  width: 6px;
  height: 6px;
  background: var(--color-copper);
  border-radius: 50%;
  opacity: 0.6;
  transition: opacity 0.25s;
}
.stat-card:hover::before,
.stat-card:hover::after {
  opacity: 1;
}
.stat-card:hover::before {
  border-color: var(--color-accent);
}
.stat-card:hover::after {
  background: var(--color-accent);
}

.stat-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
}

.stat-card__number {
  display: block;
  font-size: 2.5rem;
  font-weight: 800;
  color: var(--color-accent);
  line-height: 1.2;
}

.stat-card__suffix {
  font-size: 2.5rem;
  font-weight: 800;
  color: var(--color-accent);
}

.stat-card__label {
  display: block;
  margin-top: 4px;
  font-size: 0.9rem;
  color: var(--color-text-light);
}

/* ========================================
   Process Flow Diagram
   ======================================== */
.process-flow {
  margin-bottom: 48px;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}
.process-flow__svg {
  display: block;
  width: 100%;
  min-width: 700px;
  height: auto;
}

/* ========================================
   Capabilities
   ======================================== */
.capabilities__grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 32px;
}

.cap-card {
  background: var(--color-bg);
  border-radius: var(--radius);
  padding: 40px 32px;
  box-shadow: var(--shadow);
  position: relative;
  transition: transform 0.25s, box-shadow 0.25s;
  border-top: none;
  padding-top: 44px;
}
/* PCB 走线顶边 */
.cap-card::before {
  content: '';
  position: absolute;
  top: 12px;
  left: 20px;
  right: 20px;
  height: 4px;
  background: var(--color-accent);
  border-radius: 2px;
}
/* 过孔焊盘点 */
.cap-card::after {
  content: '';
  position: absolute;
  top: 6px;
  left: 50%;
  transform: translateX(-50%);
  width: 16px;
  height: 16px;
  background: var(--color-bg);
  border: 3px solid var(--color-copper);
  border-radius: 50%;
}

.cap-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
}

.cap-card__icon {
  font-size: 2.5rem;
  margin-bottom: 12px;
  color: var(--color-copper);
}

.cap-card__title {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: 20px;
}

.cap-card__body {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
}

.cap-card__group h4 {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--color-accent);
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: 8px;
}

.cap-card__group li {
  font-size: 0.9rem;
  color: var(--color-text-light);
  padding: 4px 0;
  padding-left: 16px;
  position: relative;
}

.cap-card__group li::before {
  content: '›';
  position: absolute;
  left: 0;
  color: var(--color-copper);
  font-weight: 700;
}

/* ========================================
   R&D / 产品研发
   ======================================== */
.rd__intro {
  max-width: 800px;
  margin: 0 auto 40px;
  text-align: center;
}
.rd__intro p {
  color: var(--color-text-light);
  margin-bottom: 12px;
  font-size: 1rem;
}

.rd__grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
}

.rd-card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 28px 24px;
  transition: transform 0.25s, box-shadow 0.25s;
  position: relative;
  overflow: hidden;
}
/* 左侧铜色走线 */
.rd-card::before {
  content: '';
  position: absolute;
  left: 0;
  top: 16px;
  bottom: 16px;
  width: 3px;
  background: var(--color-copper);
  border-radius: 0 2px 2px 0;
}
.rd-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
}

.rd-card__img {
  margin-bottom: 12px;
  border-radius: 4px;
  overflow: hidden;
  background: var(--color-bg-alt);
}
.rd-card__img svg {
  display: block;
  width: 100%;
  height: auto;
}

.rd-card__icon {
  font-size: 1.8rem;
  margin-bottom: 8px;
  color: var(--color-copper);
}

.rd-card h3 {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: 8px;
}

.rd-card p {
  font-size: 0.9rem;
  color: var(--color-text-light);
  line-height: 1.6;
}

/* ========================================
   Agency / 产品代理
   ======================================== */
.agency__grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 40px;
  align-items: start;
}
.agency__text p {
  color: var(--color-text-light);
  margin-bottom: 16px;
  font-size: 1rem;
}
.agency__cards {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
}
.agency-card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 20px 16px;
  transition: transform 0.25s, box-shadow 0.25s;
}
.agency-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
}
.agency-card__img {
  margin-bottom: 10px;
  border-radius: 4px;
  overflow: hidden;
  background: var(--color-bg-alt);
}
.agency-card__img svg {
  display: block;
  width: 100%;
  height: auto;
}
.agency-card h3 {
  font-size: 1rem;
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: 6px;
}
.agency-card p {
  font-size: 0.82rem;
  color: var(--color-text-light);
  line-height: 1.5;
}
@media (max-width: 768px) {
  .agency__grid {
    grid-template-columns: 1fr;
  }
  .agency__cards {
    grid-template-columns: 1fr 1fr;
  }
}

/* ========================================
   Certifications
   ======================================== */
.certs__grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 20px;
}

.cert-card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 32px 16px;
  text-align: center;
  transition: transform 0.25s, box-shadow 0.25s, border-color 0.25s;
  position: relative;
}
/* PCB 过孔角标 */
.cert-card::before,
.cert-card::after {
  content: '';
  position: absolute;
  width: 8px;
  height: 8px;
  background: var(--color-bg);
  border: 1.5px solid var(--color-copper);
  border-radius: 50%;
  opacity: 0.5;
  transition: opacity 0.25s, border-color 0.25s;
}
.cert-card::before { bottom: 8px; left: 8px; }
.cert-card::after  { bottom: 8px; right: 8px; }
.cert-card:hover::before,
.cert-card:hover::after {
  opacity: 1;
  border-color: var(--color-accent);
}

.cert-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
  border-color: var(--color-accent);
}

.cert-card__icon {
  font-size: 2rem;
  margin-bottom: 12px;
  color: var(--color-copper);
}
/* 证书图片卡片 */
.cert-card--img {
  padding: 16px;
}
.cert-card__img {
  width: 100%;
  height: auto;
  aspect-ratio: 3 / 4;
  object-fit: cover;
  border-radius: 4px;
  margin-bottom: 12px;
  cursor: pointer;
  transition: transform 0.25s, box-shadow 0.25s;
  border: 1px solid var(--color-border);
}
.cert-card__img:hover {
  transform: scale(1.04);
  box-shadow: var(--shadow-md);
}

.cert-card h4 {
  font-size: 1rem;
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: 6px;
}

.cert-card p {
  font-size: 0.8rem;
  color: var(--color-text-light);
}

/* ========================================
   Gallery
   ======================================== */
/* Gallery Tabs */
.gallery__tabs {
  display: flex;
  justify-content: center;
  gap: 12px;
  margin-bottom: 32px;
  flex-wrap: wrap;
}
.gallery__tab {
  padding: 8px 24px;
  border: 1px solid var(--color-border);
  border-radius: 50px;
  background: var(--color-bg);
  color: var(--color-text);
  font-size: 0.9rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.25s;
}
.gallery__tab:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
}
.gallery__tab--active {
  background: var(--color-accent);
  color: #fff;
  border-color: var(--color-accent);
}

.gallery__grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
}

.gallery__item {
  aspect-ratio: 4 / 3;
  overflow: hidden;
  border-radius: var(--radius);
  cursor: pointer;
  background: var(--color-border);
  transition: transform 0.25s, box-shadow 0.25s;
}

.gallery__item:hover {
  transform: scale(1.03);
  box-shadow: var(--shadow-md);
}

.gallery__item img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

/* 空状态 */
.gallery__grid--empty {
  display: block;
  text-align: center;
}
.gallery__empty {
  padding: 60px 20px;
  color: var(--color-text-light);
  font-size: 0.95rem;
}

/* Lightbox */
.lightbox {
  display: none;
  position: fixed;
  inset: 0;
  z-index: 2000;
  background: rgba(0, 0, 0, 0.92);
  align-items: center;
  justify-content: center;
}

.lightbox--open {
  display: flex;
}

.lightbox__img {
  max-width: 85vw;
  max-height: 80vh;
  object-fit: contain;
  border-radius: 4px;
}

.lightbox__close {
  position: absolute;
  top: 20px;
  right: 30px;
  font-size: 2.5rem;
  color: #fff;
  opacity: 0.7;
  transition: opacity 0.2s;
}
.lightbox__close:hover { opacity: 1; }

.lightbox__prev,
.lightbox__next {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  font-size: 2.5rem;
  color: #fff;
  opacity: 0.6;
  padding: 16px;
  transition: opacity 0.2s;
}
.lightbox__prev:hover,
.lightbox__next:hover { opacity: 1; }

.lightbox__prev  { left: 10px; }
.lightbox__next  { right: 10px; }

.lightbox__counter {
  position: absolute;
  bottom: 30px;
  left: 50%;
  transform: translateX(-50%);
  color: rgba(255, 255, 255, 0.7);
  font-size: 0.9rem;
}

/* ========================================
   Contact
   ======================================== */
.contact__grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 48px;
}

.contact__info h3 {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: 20px;
}

.contact__item {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  margin-bottom: 16px;
  color: var(--color-text-light);
}

.contact__icon {
  font-size: 1.2rem;
  color: var(--color-accent);
  flex-shrink: 0;
  margin-top: 2px;
}

.contact__map {
  margin-top: 24px;
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow);
}
.contact__map-img {
  width: 100%;
  height: auto;
  display: block;
}

/* Form */
.form-group {
  margin-bottom: 20px;
}

.form-group label {
  display: block;
  margin-bottom: 6px;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--color-text);
}

.required {
  color: #dc2626;
}

.form-group input,
.form-group textarea {
  width: 100%;
  padding: 10px 14px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  font-size: 1rem;
  font-family: var(--font-stack);
  transition: border-color 0.2s, box-shadow 0.2s;
  outline: none;
}

.form-group input:focus,
.form-group textarea:focus {
  border-color: var(--color-accent);
  box-shadow:
    0 0 0 3px rgba(37, 99, 235, 0.1),
    inset 0 0 0 1px rgba(199,145,72,0.15);
}

.form-group input.error,
.form-group textarea.error {
  border-color: #dc2626;
}

.form-error {
  display: block;
  margin-top: 4px;
  font-size: 0.8rem;
  color: #dc2626;
  min-height: 1.2em;
}

/* ========================================
   Footer
   ======================================== */
.footer {
  background: var(--color-primary);
  color: rgba(255, 255, 255, 0.7);
  padding: 28px 0;
  font-size: 0.9rem;
  position: relative;
}
/* 页脚顶部 PCB 走线带 */
.footer::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(
    90deg,
    transparent 0%,
    var(--color-copper) 10%,
    var(--color-copper) 20%,
    transparent 25%,
    transparent 40%,
    var(--color-accent) 45%,
    var(--color-accent) 55%,
    transparent 60%,
    transparent 75%,
    var(--color-copper) 80%,
    var(--color-copper) 90%,
    transparent 100%
  );
}

.footer__inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  text-align: center;
}
.footer__copyright {
  font-size: 0.85rem;
}
.footer__icp {
  font-size: 0.78rem;
  color: rgba(255, 255, 255, 0.5);
}
.footer__icp a {
  color: rgba(255, 255, 255, 0.5);
  transition: color 0.2s;
}
.footer__icp a:hover {
  color: var(--color-copper);
}

/* Back to Top — 过孔风格按钮 */
.back-to-top {
  position: fixed;
  bottom: 30px;
  right: 30px;
  z-index: 900;
  width: 44px;
  height: 44px;
  background: var(--color-accent);
  color: #fff;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  box-shadow: var(--shadow-md);
  opacity: 0;
  visibility: hidden;
  transition: all 0.3s;
}
/* 过孔外环 */
.back-to-top::after {
  content: '';
  position: absolute;
  top: -6px;
  left: -6px;
  right: -6px;
  bottom: -6px;
  border: 2px solid var(--color-copper);
  border-radius: 50%;
  opacity: 0.5;
  transition: opacity 0.3s;
}
.back-to-top--show {
  opacity: 1;
  visibility: visible;
}
.back-to-top:hover {
  background: #1d4ed8;
  transform: translateY(-3px);
}
.back-to-top:hover::after {
  opacity: 1;
}

/* Toast */
.toast {
  position: fixed;
  top: 90px;
  right: 30px;
  z-index: 3000;
  padding: 14px 24px;
  border-radius: var(--radius);
  color: #fff;
  font-size: 0.95rem;
  font-weight: 500;
  transform: translateX(120%);
  transition: transform 0.35s cubic-bezier(0.25, 0.46, 0.45, 0.94);
  max-width: 380px;
}

.toast--show {
  transform: translateX(0);
}

.toast--success { background: #059669; }
.toast--error   { background: #dc2626; }

/* ========================================
   Responsive — max-width: 768px
   ======================================== */
@media (max-width: 768px) {

  /* Navigation */
  .nav__hamburger { display: flex; }
  .nav__logo-img { height: 34px; mix-blend-mode: multiply; filter: contrast(1.05) saturate(1.1); }

  .nav__menu {
    position: fixed;
    top: var(--nav-height);
    left: 0;
    width: 100%;
    background: rgba(255, 255, 255, 0.98);
    backdrop-filter: blur(8px);
    flex-direction: column;
    gap: 0;
    padding: 16px 0;
    transform: translateY(-120%);
    transition: transform 0.35s;
    box-shadow: var(--shadow);
  }

  .nav__menu--open {
    transform: translateY(0);
  }

  .nav__link {
    display: block;
    padding: 14px 24px;
    text-align: center;
  }

  /* Hero */
  .hero__title {
    font-size: 1.8rem;
    letter-spacing: 1px;
  }

  .hero__subtitle {
    font-size: 1rem;
  }

  /* Section */
  .section {
    padding: 60px 0;
  }

  .section__title {
    font-size: 1.5rem;
  }

  /* About */
  .about__grid {
    grid-template-columns: 1fr;
    gap: 32px;
  }

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

  .stat-card__number,
  .stat-card__suffix {
    font-size: 2rem;
  }

  /* R&D */
  .rd__intro {
    margin-bottom: 28px;
  }
  .rd__grid {
    grid-template-columns: 1fr;
  }

  /* Capabilities */
  .capabilities__grid {
    grid-template-columns: 1fr;
  }

  .cap-card__body {
    grid-template-columns: 1fr;
  }

  /* Certifications */
  .certs__grid {
    grid-template-columns: repeat(3, 1fr);
  }
  .cert-card--img {
    grid-column: span 1;
  }
  .cert-card__img {
    aspect-ratio: 2 / 3;
  }

  /* Gallery */
  .gallery__tab {
    padding: 6px 16px;
    font-size: 0.8rem;
  }
  .gallery__grid {
    grid-template-columns: repeat(2, 1fr);
  }

  /* Contact */
  .contact__grid {
    grid-template-columns: 1fr;
  }

  /* Footer */
  .footer__inner {
    flex-direction: column;
    gap: 6px;
    text-align: center;
  }

  /* Back to top */
  .back-to-top {
    bottom: 20px;
    right: 20px;
    width: 40px;
    height: 40px;
  }
}