body {
  font: 10px sans-serif;
}

#chart{
  margin: 20px;
  background: #eee;
  border: 1px solid #222;
}

.x-axis-layer line, .y-axis-layer line,
.x-axis-layer path, .y-axis-layer path {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
}

.arrow {
  stroke: #000;
  stroke-width: 1.5px;
}

.outer,
.inner {
  shape-rendering: crispEdges;
}

.outer {
  fill: none;
  stroke: #000;
}

.inner {
  fill: #ccc;
  stroke: #000;
  stroke-dasharray: 3, 4;
}