html, body {
  height: 100%;
  margin: 0;
  padding: 0;
  width: 100%;
}

header {
  background-color: rgba(100,100,100,0.25);
  font-size: 0.8em;
  padding: 0.5em;
  position: absolute;
  width: 100%;
}

svg {
  cursor: crosshair;
  height: 100%;
  position: absolute;
  stroke: #bbb;
  stroke-width: 1;
  width: 100%;
}

path {
  fill: none;
  stroke: #00f;
  stroke-linecap: round;
  stroke-width: 5;
}