#editor { 
  position: absolute;
  top: 0;
  right: 50%;
  bottom: 0;
  left: 0;
}

#math-wrap {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 50%;

  margin: 10px;
}

#buttons {
  position: absolute;
  bottom: 10px;
  right: 10px;
  left: calc(50% + 10px);
}