.page-container {
  background-image: url('../../assets/images/start_bg.png');
  background-repeat: no-repeat;       /* 禁止重复 */
  background-size: 100% 106%;         /* 宽高铺满容器 */
  background-position: center;        /* 居中显示 */
  width: 100vw;
  height: 100vh;
  box-sizing: border-box;
}