Untitled fiddle

HTML

<div class="root">
  <div class="menubar">Menubar</div>
  <div class="editor">Editor</div>  
  <div class="statusbar">Statusbar</div>
</div>

CSS

* {
  margin: 0;
  padding: 0;
}

html {
  background: black;
  color: white;
  font: 12pt system-ui;
  text-align: center;
}

.root {
  display: grid;
  grid-template-rows: 2em 1fr 2em;
  height: 100vh;
}

.menubar, .statusbar {
  background: #243162;
}