body {
  background-image: url('inside_center.jpeg'); /* swap with your image filename */
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
  min-height: 100vh;
  margin: 0;
}
.dot {
      position: absolute;
      top: 35%;
      left: 50%;
      width: 20px;
      height: 20px;
      background-color: red;
      border-radius: 50%;
      display: block;
    }

    .dot:hover {
      background-color: darkred;
      cursor: pointer;
    }