body {
  margin: 0;
  height: 100vh;
}

#header {
  height: 50px;
  padding: 5px;
}

#runButton {
  position: absolute;
  left: 50%;
}

#app {
  height: calc(100% - 50px);
}

.column {
  width: 50%;
  height: 100%;
  float: left;
}