/* == BASE STYLES == */


body {
    font-family: 'Poppins', sans-serif;
    background-color: #f0f4f8;
    color: #023e8a;
    margin: 0;
    padding: 0;
    overflow-x: hidden;
  }
  
  html {
    scroll-behavior: smooth;
    font-size:50%; /* 1rem = 10px */
  }
  
  /* == NAVBAR == */
  .navbar {
    position: fixed;
    top: 0;
    width: 100%;
    height: 90px;
    background: rgb(0, 0, 0, 0.5); /* ✅ 半透明黑色背景 */
    box-shadow: none;
    z-index: 1000;
    font-size: 3rem;              /* ✅ 建议保留这个，覆盖前面30px */
    color: white;
    font-weight: 300;
    font-family: 'Poppins', sans-serif;
  }
  
  .navbar .logo img {
    height:30px;
    width: auto;
    transition: all 0.3s ease-in-out;
  }
  
  #mobile-menu {
    transition: all 0.3s ease-in-out;
  }
  
/* 让 nav-link 可高亮显示 */

.nav-link:hover {
  background-color:  #1e67b0;
}

.nav-link.active {
  background-color: #0d437e; /* 浅蓝色背景 */
  color: white;             /* 深蓝字体 */
  font-weight: 600;
}

.navbar li:hover > ul {
  display: block;
}
.navbar ul li ul {
  display: none;
  position: absolute;
}

/* 下拉菜单容器 */
.submenu {
  background-color: #1f2937; /* 深灰（Tailwind 的 gray-800） */
  border-radius: 0px;
  padding: 10px 14px;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
  z-index: 999;
}

/* 下拉菜单链接样式 */
.submenu a {
  display: block;
  color: white; /* ✅ 白色字体 */
  padding: 8px 20px;
  text-decoration: none;
  transition: background-color 0.2s;
  border-radius: 0px;
}

/* 鼠标悬停效果 */
.submenu a:hover {
  background-color: #374151; /* 灰色 hover（Tailwind gray-700） */
}


 /* == VIDEO HERO == */
 .video-hero {
  position: relative;
  width: 100%;
  height: 80vh;
  display: flex;
  justify-content: center;
  align-items: center;
  overflow: hidden;
}

#background-video {
  width: 100%;
  height: 90vh;
  object-fit: cover;
  position: absolute;
  top: 0;
  left: 0;
  z-index: -1;
}

.video-overlay {
 position: absolute;
 top: 120px;         /* 控制 overlay 离底部多远（Y轴位置） */
 left:15%;              /* 控制 overlay 的水平位置（X轴，百分比） */
                         /* 用来居中，但配合 left: 20% 会导致偏移 */
 width: 80%;             /* 控制宽度，占整个屏幕的百分比 */
 
 padding: 30px;           /* 内容与边框的内边距 */
 background: rgba(255, 255, 255, 0);  /* 背景透明色 */
 border-radius: 0px;     /* 圆角 */
 display: flex;
 flex-direction: column;
 align-items: left;
 text-align:left;
 opacity: 1;
 animation: none;
 z-index: 1;
}

.overlay-logo img {
  width: 210px; /* ✅ 适中大小 */
  height: auto;
}

.video-overlay h1 {
  font-size: 4.5rem;
  max-width: 1000px;
  line-height: 1.4; /* ✅ 增加行间距，推荐范围 1.4 ~ 1.8 */
  color: white;
  margin-bottom: 10px;
  font-weight: 500;
}

.video-overlay p {
  font-size: 3.2rem;
  max-width: 1200px;
  line-height: 1.2; /* ✅ 增加行间距，推荐范围 1.4 ~ 1.8 */
  text-align: left;
  color: white;
  margin-bottom: 20px;
  font-weight: 300;
}


.read-more {
  display: inline-block;
  padding: 12px 50px;
  max-width: 500px; /* 限制最大宽度 */
  font-size: 2rem;
  text-align:left;
  color: white;
  background: linear-gradient(90deg, #16898d, #1e67b0);
  text-decoration: none;
  border-radius: 0;
  transition: all 0.3s ease;
}

.read-more:hover {
  background: linear-gradient(90deg, #16898d, #1e67b0);
  transform: scale(1.05);
}



/* Section整体  company*/
/* Section整体容器 */
.company-flex-wrapper {
  display: flex;
  flex-direction: column; /* ⬅ 永远一栏 */
  align-items: center;
  gap: 30px;
  max-width: 1400px;
  width: 100%;
  margin: 0 auto;
  padding: 60px 40px;
}

.left-column,
.right-column {
  width: 100%;
  max-width: 100%;
  text-align: center;
}



/* 左栏标题样式 */
.heading-tech {
  font-size: 3.2rem;
  font-weight: 600;
  color: #1e67b0;
  line-height: 1.2;
  text-align: left;
  background: linear-gradient(90deg, #16898d, #5ba59b, #36a5ee, #1e96f8,  #1e67b0);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
   /* 兼容性处理 */
   background-clip: text;
   color: transparent;


}

/* 右栏段落样式 */
.custom-paragraph {
  font-size: 2.5rem;
  font-weight: 400;
  color: #1e67b0;
  line-height: 1.2;
  text-align: justify;
}



/*our company 第二段容器 */
.image-block {
  position: relative;
  width: 100%;
  min-height: 500px;
  overflow: hidden;
  margin-top:-100px;
}

/* 背景图片 */
.our-company-image {
  position: absolute;
  left: 0;
  width: 100%;
  height: 50%;
  object-fit: cover;
  z-index: 0;
  top:100px
}

/* 容器内部居中对齐 */
.caption-wrapper {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  max-width: 1000px;
  padding: 15px;
  text-align: left;
}

/* 覆盖在图片上的文字容器 */
.overlay-text {
  position: absolute;
  inset: 0;
  display: flex;
  justify-content: left;
  align-items: center;
  z-index: 1;
  width: 80%;
  height: 500px;
  left:15%;
}


/* 第一段文字 - 大标题 */
.caption-line1 {
  font-size: 4.5rem;
  color: white;
  font-weight: 400;
  margin-bottom: 20px;
  line-height: 1.2;
}

/* 第二段文字 - 小标题斜体 */
.caption-line2 {
  font-size: 3.5rem;
  color: white;
  font-style: normal;
  font-weight: 300;
  line-height: 0.9;
}



  /* technology */
  /* 替换掉原 .additional-text */
  #technology {
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 50px 0;
    text-align: center;
    margin-top:-150px;
  }
  
  #technology h2 {
    font-size: 2.8rem;
    font-weight: 600;
    color: #1e67b0;
    max-width: 80%;
    margin: 0 auto;
    line-height: 1.6;
  }

  #technology .custom-paragraph {
    font-size: 2rem;
    font-weight: 400;
    color: #1e67b0;
    max-width: 70%;
    text-align: justify;
    margin: 0 auto 20px;
    line-height: 1.2; /* 行间距调整就在这里 */
  }

  .technology-video-container {
    width: 80%;
    max-width: 1200px;
    margin: 0px auto;
    border-radius: 0px;
    overflow: hidden;
  }
  
  .technology-video {
    width: 100%;
    height: auto;
    display: block;
    border-radius: 0px;
  }
  
   /* == project section == */
  .cards-section {
    margin-top: 120px;
    padding: 0 20px;
    text-align: center;
  }
  
  .cards-intro-text h2 {
    font-size: 2.8rem;
    font-weight: 600;
    color: #1e67b0;
    margin-bottom: 10px;
    text-align: center; 

  }
  
  .cards-intro-text p {
    font-size: 2rem;
    font-weight: 400;
    color: #1e67b0;
    max-width: 1200px;
    margin: 0 auto 50px auto;
    line-height: 1.4;
    text-align: justify;
    max-width:80%;
  }
 
/* == CARDS == */
.card-container {
  display: flex;
  flex-direction: column;       /* 让卡片上下排列 */
  align-items: center;          /* 水平居中卡片内容 */
  gap: 20px;                    /* 卡片之间的垂直间距 */
  width: 100%;
  margin-top: 30px; /* ✅ 和上个单元的间距 */
}

.card {
  display: flex;
  width: 100%;
  height: 380px;
  overflow: hidden;
  border-radius: 0;
  box-shadow: none;
  position: relative;
  /* 移除 margin-top: 200px;，使用 gap 更优雅 */
}



.card video {
  width:100%;
  height: 100%;
  object-fit: cover;
}

.card .overlay {
  position: absolute;
  top: 0px;
  width: 60%;
  height: 100%;
  padding: 30px;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  justify-content: flex-start;
  color: white;
}

#card1 .overlay {
  right: 0px;
  background: rgba(0, 0, 0, 0.5);
}

#card2 .overlay {
  left: 0px;
  background:  rgba(0, 0, 0, 0.5);
}

.overlay h3 {
  font-size: 2.2rem;
  font-weight: bold;
  margin-top: -10px;
  line-height: 1.2;
  text-align: left;

}

.overlay p {
  font-size: 1.7rem;
  margin-bottom: 5px;
  line-height: 1.0;
  text-align: justify;
}

.learn-more-card {
  display: flex;
  align-items: center;
  font-size: 1.5rem;
  font-weight: bold;
  color:  white;
  text-decoration: none;
  margin-top: auto;
  transition: 0.3s;
}

.learn-more-card:hover {
  color: #007bff;
}

.learn-more-card::before {
  content: "▶";
  font-size: 1.5rem;
  color: #16898d;
  margin-right: 8px;
}

.card:hover {
  transform: translateY(-5px);
  box-shadow: 0 8px 16px rgba(0, 0, 0, 0.2);
}
  



  /*Research development */
  #Research-development {
    padding-top: 300px;
    background: rgba(0,0,0, 0.05); /* 如果你想让这块也有背景 */
    margin-bottom:0;
    margin-top:-200px;
    
  }
  
  
  .research-container {
    display: grid;
    gap: 20px;
    width: 100%;
    padding: 40px 0; /* ⚠️ 不要用 400px */
    text-align: center;
    margin-bottom:0;
    
  }
  
  .research-container h2 {
    font-size: 4.2rem;
    font-weight: 100;
    color: #1e67b0;
    text-align:center;          /* ✅ 文字两端对齐 */
    max-width: 80%;               /* ✅ 控制宽度 */
    margin: 0 auto;               /* ✅ 居中这个文字块 */
    letter-spacing: 0.5px;
    line-height: 1.2;             /* ✅ 行间距（可调） */
  }


  .publication-overlay {
    background: transparent; /* 或其他你想要的背景色 */
    padding: 30px 40px;  /* ✅ 内容与边框的间距：上下 30px，左右 40px */
    width: 75%;          /* ✅ 减小整体宽度，适度留白 */
    margin: 40px auto;   /* ✅ 与其他内容的上下距离 */
    border-radius: 0px; /* ✅ 如果你想要圆角 */
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0); /* ✅ 阴影可选 */
    text-align: left;    /* ✅ 文本对齐方式 */
  }
  
  /* Publications 小标题样式 */
  .pub-title {
    font-size: 2.5rem;
    font-weight: bold;
    color: #023e8a;
    text-align: left;
    margin-bottom: 50px; /* ✅ 增加标题与段落之间的间距 */
  }
  

/* Publications 段落样式 */
.publication-text {
  font-size: 2rem;
  line-height: 1;
  color: #444;
  text-align: left;
  margin-left: 0;
  margin-right: 0;
  max-width: 100%; /* ✅ 占满父级容器 */
  padding-left: 0;  /* 可根据需要微调 */
  
  /* 👇 新增：两栏布局 */
  columns: 2;
  column-gap: 40px; /* 两栏之间的间距 */
}



/* 日期加深并斜体 */
.publication-text .date {
  font-weight: bold;
  font-style: italic;
  color: #1c67af;
}

.collapsed {
  max-height: 600px;
  overflow: hidden;
}

.read-more-toggle {
  background: none;
  border: none;
  color: #1e67b0;
  font-weight: bold;
  font-style: italic;
  cursor: pointer;
  font-size: 1.8rem;
  margin-top: 20px;
  display: flex;
  align-items: center;
  gap: 6px;
}

.read-more-toggle:hover {
  color: #007bff;
}






/* Contact 视频背景区域 */
.video-bg {
  position: relative;
  width: 100%;
  height: 700px; /* ✅ 缩短高度 */
  overflow: hidden;
  z-index: 0;
  margin: 0; /* ✅ 去除上下负 margin */
}

.video-bg video {
  width: 100%;
  height: 100%;
  object-fit: cover;
}



/* Contact 内容居中覆盖 */
.contact-content {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%; /* ✅ 跨满 */
  height: 100%; /* ✅ 撑满容器高度 */
  display: flex;
  flex-direction: column;
  justify-content: center; /* ✅ 垂直居中 */
  align-items: center;     /* ✅ 水平居中 */
  text-align: center;
  padding: 20px;
  z-index: 1;
  background: rgba(0,0,0,0); /* 可选遮罩层 */
}




.contact-content h2 {
  font-size: 3rem;
  margin-bottom: 40px;
  margin-top:50px;
  font-weight: bold;
  color:white;
}

.contact-content p {
  font-size: 2.5rem;
  margin-bottom:30px;
  font-weight: 300;
  color:white;
}


/* 表单布局 */
.form-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  width: 100%;
  max-width: 900px;   /* ✅ 控制最大宽度 */
  margin: 0 auto;     /* ✅ 居中 */
  padding: 0 20px;    /* ✅ 加内边距避免贴边 */
}

@media (max-width: 768px) {
  .form-grid {
    grid-template-columns: 1fr;  /* 小屏改为单列 */
  }

  .form-grid button {
    grid-column: span 1;
  }
}

.form-grid textarea {
  grid-column: span 2;
  min-height: 150px;
  resize: none;
}

.form-grid input,
.form-grid textarea {
  padding: 15px;
  border: none;
  border-radius: 5px;
  font-size: 1rem;
  width: 100%;
}

.btn {
  grid-column: span 2;
  background: linear-gradient(90deg, #16898d, #1e67b0);
  color: white;
  font-size: 1.2rem;
  padding: 12px;
  border: none;
  border-radius: 5px;
  cursor: pointer;
}

.btn:hover {
  background-color: #0056b3;
}

/* 联系方式图标 */
.contact-icons {
  display: flex;
  justify-content: center;
  gap: 180px;
  margin-top: 20px;
  margin-left:20px;
  margin-right:20px;
}

.icon-box {
  display: flex;
  flex-direction: column;
  align-items: center;
  color: white;
}

.icon-box img {
  width: 50px;
  height: 50px;
  margin-bottom: 10px;
  transition: transform 0.3s ease;
  
}

.icon-box p {
  font-size: 1.5rem;
  text-align: center;
  line-height: 1.4;
}

.icon-box img:hover {
  transform: scale(1.25);
}



 .lightbox {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.85);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    animation: fadeIn 0.5s ease-out;
  }
  
  .lightbox.hidden {
    display: none;
  }
  
  .lightbox img {
    max-width: 90%;
    max-height: 80%;
    border-radius: 10px;
    box-shadow: 0 0 15px rgba(255,255,255,0.2);
  }
  
  .close-btn {
    position: absolute;
    top: 20px;
    right: 30px;
    font-size: 30px;
    color: white;
    cursor: pointer;
  }


  /* == FOOTER == */
  .footer {
    background-color: #023e8a;
    color: white;
    text-align: center;
    padding: 10px 0;
    margin-bottom: -40px;
    border: none;
    width: 100%;
  }
  
  .footer p {
    font-size: 1.5rem;
  }
  
  /* == ANIMATIONS == */
  .fade-in {
    opacity: 0;
    animation: fadeIn 1.5s ease-out forwards;
  }
  
  @keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
  }
  
  /* == MEDIA QUERIES == */
  @media (max-width: 768px) {
    .card-container {
      flex-direction: column;
    }
  
    .navbar {
      padding: 10px;
    }
  
    .form-grid {
      grid-template-columns: 1fr;
    }
  
    .form-grid button {
      grid-column: span 1;
    }
  
    .square-images {
      grid-template-columns: 1fr;
    }
  }
  
  @media (max-width: 480px) {
    html {
      font-size: 45%; /* 手机端进一步缩小基准字体大小 */
    }
  
    .navbar {
      font-size: 2.5rem;
    }
  
    .video-overlay h1 {
      font-size: 3.2rem;
      line-height: 1.4;
    }
  
    .video-overlay p {
      font-size: 2rem;
    }
  
    .read-more {
      font-size: 1.8rem;
      padding: 10px 30px;
    }
  
    .caption-line1 {
      font-size: 3.2rem;
    }
  
    .caption-line2 {
      font-size: 2.2rem;
      line-height: 1.2;
    }
  
    .contact-content h2 {
      font-size: 2.4rem;
      margin-top: 30px;
    }
  
    .contact-content p {
      font-size: 1.8rem;
    }
  
    .form-grid {
      padding: 0 10px;
      gap: 15px;
    }
  
    .contact-icons {
      flex-direction: column;
      gap: 25px;
    }
  
    .icon-box img {
      width: 40px;
      height: 40px;
    }
  
    .icon-box p {
      font-size: 1.2rem;
    }
  
    .publication-text {
      columns: 1; /* 单栏显示论文文字 */
    }
  }