/*GENERAL*/

* {
  box-sizing: border-box;
}

body  {
  font-family: helvetica;
  background: #ccc;
}

.container {
  max-width: 700px;
  margin: 0 auto;
}

h1 {
  text-align: center;
  margin: 30px 0;
}

/*TEXT DIVS*/

.textbox-container {
  position: relative;
}

.editable-div,
.mirror-div {
  font-family: monospace;
  font-size: 16px;
  line-height: 1.4em;
  background: #fafafa;
  min-height: 400px;
  width: 100%;
  padding: 1em;
  margin-bottom: 10px;
}

.editable-div:focus {
  outline: 2px solid #81afe4;
}

.editable-div {
  /* let the highlights show through from the mirror div, behind it */
  background: transparent;
  position: relative;
}

.mirror-div {
  /* hide the redundant text, since only the highlights need to show through*/
  color: transparent;
  position: absolute;
  top: 0;
}

.highlight {
  background: #aaddff;
}