body {
    padding: 0;
    margin: 0;
    width: 100vw;
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
}

canvas {
    position: absolute;
}
.popup-button {
  display:flex;
  position: fixed;
  top: 20px;
  right: 20px;
  padding: 10px 20px;
  background-color: #00ff00;
  color: #fff;
  border: none;
  border-radius: 5px;
  cursor: pointer;
  font-size: 16px;
  z-index: 1000;
}