styles.css

body {
  height: 100%;
  padding: 0;
  margin: 0;
  font-family: Tahoma, Verdana;
  font-size: 14px;
  display: flex;
  justify-content: center;
  background: #DDD;
}

section {
  background: #FDFDFD;
  margin: 0 3rem;
  padding: 0 2rem;
  flex-grow: 0;
}

table {
  border-spacing: 0;
  border-top: 1px solid #999;
  border-right: 1px solid #999;
  font-size: 80%;
}

input, button {
  font-size: 125%;
  padding: 0 0.25rem;
}

button {
  cursor: pointer;
  background: #DDD;
  border: 1px solid #CCC;
  border-radius: 0.25rem;
}


td {
  padding: 0.1rem 0.4rem;
  border-left: 1px solid #bbb;
  border-bottom: 1px solid #bbb;
}

td.spacer {
  padding: 0;
  width: 2px;
  background: #BBB;
}

svg {
  margin-left: 0.5rem;
  border: 1px solid #bbb;
  display: none;
}


.links line {
  stroke: #999;
  stroke-opacity: 0.6;
}

.nodes circle {
  stroke: #fff;
  stroke-width: 2px;
}