html, body {
  height: 96%;
}

html {
  display: table;
  margin: auto;
}

body {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
}

audio {
  display: none;
  left: 10px;
  bottom: 10px;
  width: calc(100% - 20px);
}

audio.playing {
  position: fixed;
  left: calc(40%);
  top: calc(38%);
  bottom: 0;
  width: 20%;
}

#file {
  display: none;
  top: 10px;
  left: 10px;
}

label {
  background-color: #3498db;
  border-radius: 5px;
  color: #fff;
  cursor: pointer;
  margin: 10px;
  padding: 6px 20px;
}

#canvas {
  position: fixed;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  z-index: -1;
}