body {
  margin: 0;
  padding: 0;
  width: 100vw;
  height: 100vh;
  overflow: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: #ececec;
}

button{
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    overflow: auto;
    background: none;
    border: none;
    outline: none;
    appearance: none;
    z-index:  100;
}
canvas {
  max-width: 100%;
  max-height: 100%;
}