html,
body {
  margin: 0;
  padding: 0;
}

body {
  height: 100vh;
}

#container {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}

#toolbar {
  position: absolute;
  left: 0;
  top: 0;
  padding: 16px;
  z-index: 5;
  background-color: white;
}

#toolbar > a {
  display: inline-block;
  width: 24px;
  height: 24px;
  padding: 8px;
  cursor: pointer;
  position: relative;
}

input[type="file"] {
  opacity: 0;
  position: absolute;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
}

canvas {
  display: block;
}