style.css

.display_stage {
    position: fixed;
    background: #900;
    left: 5vw;
    top: 2vh;
    height: 94vh;
    width: 90vw;
    background-color: black;
    border-radius: 15px;
    border: 1vh solid #D0D0D0;
    z-index: 0;
}

#canvas1, #canvas2, #backCanvas1,#backCanvas2 {
  display: block;
    margin: 0 auto;
}

.leftbox {
  width: 600px;
  height: 600px;
  position:absolute;
  top:50%;
  left:50%;
  margin-right:-50%;
  transform: translate(-110%,-50%);
}

.rightbox {
  width: 600px;
  height: 600px;
  position:absolute;
  top:50%;
  left:50%;
  margin-right:-50%;
  transform: translate(10%,-50%);
}

.response_div {
  width: 40w;
  height: 8vw;
  position:absolute;
  top:50%;
  left:50%;
  margin-right:-50%;
  transform: translate(-50%,140%);
}

.response_button {
  width: 10vw;
  height: 10vw;
  background: #505050;
  margin: 1vw;
  position: relative;
  color: #fff;
  border-radius:15px;
  font-size: 24px;
  vertical-align:top;
}

.response_button:hover {
  color: red;
}

.response_button:active {
  background-color: black;
}

.response_button_key {
  width: 10vw;
  height: 10vw;
  background: #505050;
  margin: 1vw;
  position: relative;
  color: #fff;
  border-radius:15px;
  font-size: 24px;
  vertical-align:top;
}

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

.fixation {
  color: grey;
}