* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: "Microsoft YaHei", sans-serif;
  scroll-behavior: smooth;
}
body {
  background: #fff;
}
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
}

/* 头部导航 */
.header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 70px;
  background: #003366;
  z-index: 999;
  transition: height 0.3s ease;
}
.header .container {
  display: flex;
  align-items: center;
  height: 100%;
}

/* LOGO */
.logo img {
  height: 56px;
  max-height: 60px;
  width: auto;
  display: block;
  margin-top: 3px; /* 微调垂直居中，适配70px高的导航栏 */
  filter: brightness(1.45);  /* 提亮15%，自然不刺眼 */
}

/* 主导航 */
.nav {
  display: flex;
  list-style: none;
  margin: 0 auto;
}
.nav li {
  position: relative;
  padding: 0 20px;
}
.nav li a {
  color: #fff;
  text-decoration: none;
  font-size: 16px;
  line-height: 70px;
  display: block;
}
.nav li a:hover {
  color: #ff6600;
}

/* 产品中心下拉菜单 */
.nav_sub .sub_menu {
  position: absolute;
  top: 100%;
  left: 50%;
  transform: translateX(-50%);
  width: 200px;
  background: #fff;
  box-shadow: 0 2px 10px rgba(0,0,0,0.1);
  border-radius: 4px;
  opacity: 0;
  visibility: hidden;
  transition: all 0.3s;
}
.nav_sub:hover .sub_menu {
  opacity: 1;
  visibility: visible;
}
.sub_menu a {
  color: #333 !important;
  line-height: 42px !important;
  padding: 0 15px;
  font-size: 15px !important;
  text-align: center;
}
.sub_menu a:hover {
  background: #f5f5f5;
  color: #ff6600 !important;
}

/* 询价按钮 */
.nav_btn {
  background: #ff6600;
  color: #fff;
  padding: 8px 20px;
  border-radius: 3px;
  text-decoration: none;
  font-size: 15px;
}

/* 轮播 */
.banner {
  margin-top: 70px;
  height: 500px;
  position: relative;
}
.banner-mask {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.15);
  z-index: 1;
}
.banner-item {
  position: absolute;
  width: 100%;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  color: #fff;
  opacity: 0;
  transition: 1s;
}
.banner-item.active {
  opacity: 1;
}
.banner-item:nth-child(1) {
  background: linear-gradient(to right, #003366, #0055aa);
}
.banner-item:nth-child(2) {
  background: linear-gradient(to right, #004488, #0066cc);
}
.banner-inner h2 {
  font-size: 40px;
  margin-bottom: 15px;
}
.banner-inner p {
  font-size: 18px;
  margin-bottom: 25px;
}
.banner-btn {
  background: #ff6600;
  color: #fff;
  padding: 12px 30px;
  border-radius: 3px;
  text-decoration: none;
}

/* 产品模块 */
.product_section,
.about_section,
.contact_section {
  padding: 70px 0;
}
.tit {
  font-size: 28px;
  color: #003366;
  text-align: center;
  margin-bottom: 40px;
  position: relative;
}
.tit::after {
  content: "";
  width: 50px;
  height: 3px;
  background: #ff6600;
  position: absolute;
  left: 50%;
  bottom: -10px;
  transform: translateX(-50%);
}

.product_list {
  display: flex;
  flex-wrap: wrap;
  gap: 30px;
  justify-content: center;
}
.product_list .item {
  width: 320px;
  background: #f7f9fc;
  padding-bottom: 20px;
  border-radius: 6px;
  overflow: hidden;
  text-align: center;
}
.product_list img {
  width: 100%;
  height: 220px;
  object-fit: cover;
  margin-bottom: 15px;
}

.about_content {
  max-width: 900px;
  margin: 0 auto;
  text-align: center;
  line-height: 1.9;
  color: #444;
}
.contact_section {
  text-align: center;
  line-height: 2;
  font-size: 16px;
}

/* 弹窗 */
.modal {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0,0,0,0.6);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 1000;
}
.modal.show {
  display: flex;
}
.modal_box {
  background: #fff;
  padding: 30px;
  width: 90%;
  max-width: 500px;
  border-radius: 6px;
  position: relative;
}
.close {
  position: absolute;
  right: 20px;
  top: 15px;
  font-size: 24px;
  cursor: pointer;
}
.modal_box form {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-top: 20px;
}
.modal_box input,
.modal_box textarea {
  padding: 10px;
  border: 1px solid #ddd;
  border-radius: 3px;
}
.modal_box button {
  background: #003366;
  color: #fff;
  padding: 10px;
  border: none;
  border-radius: 3px;
  cursor: pointer;
}

/* 回到顶部 */
.back_top {
  position: fixed;
  right: 30px;
  bottom: 30px;
  width: 45px;
  height: 45px;
  background: #003366;
  color: #fff;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 20px;
  opacity: 0;
  visibility: hidden;
  transition: 0.3s;
}
.back_top.show {
  opacity: 1;
  visibility: visible;
}
/* 轮播遮罩 —— 只压暗图片，不影响文字 */
.banner-item {
  position: absolute;
  width: 100%;
  height: 100%;
  top: 0;
  left: 0;
  opacity: 0;
  transition: opacity 1s ease;
}
.banner-mask {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.15); /* 这里自由调透明度 */
  z-index: 1;
}
.banner-inner {
  position: relative;
  z-index: 2; /* 文字在遮罩上方，不会被盖住 */
}
.page-container {
  max-width: 1200px;
  margin: 100px auto 60px;
  padding: 0 20px;
}
.page-title {
  text-align: center;
  margin-bottom: 40px;
  padding-bottom: 15px;
  border-bottom: 1px solid #eee;
}
.page-title h1 {
  font-size: 28px;
  color: #003366;
  font-weight: normal;
}
.page-content p {
  font-size: 16px;
  line-height: 2;
  color: #333;
  margin-bottom: 24px;
  text-align: center;    /* 改为居中对齐 */
  text-indent: 0;        /* 去掉缩进 */
}