style.css

.display_stage {
    position: fixed;
    background: black;
    left: 5vw;
    top: 2vh;
    height: 94vh;
    width: 90vw;
    border-radius: 15px;
    border: 1vh solid #D0D0D0;
    z-index: 0;
}

.display_stage > div, .display_stage > p {
  color: white;
}

.centerimg {
  width: 100%;
  height: 100%;
  position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    display: flex;
    justify-content: center; /* align horizontal */
    align-items: center; /* align vertical */
    margin-left: auto;
    margin-right: auto;
}

.leftbox {
  width: 22vw;
  height: 22vw;
  position:absolute;
  top:50%;
  left:50%;
  margin-right:-50%;
  transform: translate(-100%,-50%);
  z-index: 2;
}

.distractorbox {
  width: 22vw;
  height: 22vw;
  position:absolute;
  top:50%;
  left:50%;
  margin-right:-50%;
  transform: translate(-105%,-57%);
}

.rightbox {
  width: 22vw;
  height: 22vw;
  position:absolute;
  top:50%;
  left:50%;
  margin-right:-50%;
  transform: translate(0%,-50%);
}

.mask {
  width: 80%;
}

img {
  height: 100%;
  width: 100%;
}

.fb_box {
  width:35vw;
  height: 20vh;
  position:absolute;
  top:50%;
  left:50%;
  margin-right:-50%;
  transform: translate(-50%,-175%);
}