core/packages/template-explorer/style.css

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
}

#header {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 60px;
  box-sizing: border-box;
  background-color: #1e1e1e;
  border-bottom: 1px solid #333;
  padding: 0.3em 1.6em;
  color: #fff;
}

h1 {
  font-size: 18px;
  display: inline-block;
}

#options {
  float: right;
  margin-top: 1em;
}

.options-group {
  margin-right: 30px;
}

#header span, #header label, #header input {
  display: inline-block;
}

#header .label {
  font-weight: bold;
}

#header input {
  margin-left: 12px;
  margin-right: 6px;
}

#header label {
  color: #999;
}

.editor {
  position: absolute;
  top: 60px;
  bottom: 0;
  box-sizing: border-box;
}

#source {
  left: 0;
  width: 45%;
}

#output {
  left: 45%;
  width: 55%;
}

.highlight {
  background-color: rgba(46, 120, 190, 0.5);
}