* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: "微软雅黑", sans-serif;
  }
  
  body {
    background-image: url('../image/backgroud.png');
    background-repeat: no-repeat; /* 不重复平铺 */
    background-size: 100% 25%; /* 修改：水平自动伸缩，垂直填满 */
    background-color: #f4f9f9;
    min-height: 100vh;
    padding-bottom: 60px; /* 给底部导航留空间 */
  }

  /* 顶部导航栏 */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  padding: 15px 20px;
  color: #fff;
  position: relative;
}

/* 注册子导航 */
.sub-nav {
  display: flex;
  align-items: center;
  margin-top: 10px;
  padding-left: 5px;
  position: relative;
}

.sub-nav-back {
  font-size: 20px;
  cursor: pointer;
  margin-right: 10px;
}

.sub-nav-title {
  font-size: 20px;
  font-weight: 400;
  position: absolute;
  left: 50%;
  transform: translateX(-50%);
}