body #main_box_container {
  width: 100%;
  height: 80vh;
  display: flex;
  flex-direction: row;
  justify-content: center;
  align-items: center;
}
body #main_box_container #main_box {
  width: 500px;
  height: 50px;
  background: #FFFFFF;
  padding: 30px;
}