<div class="parent">
  <header>Header</header>
  <div class="left-side">Left Sidebar</div>
  <main>Main Content</main>
  <div class="right-side">Right Sidebar</div>
  <footer>Footer</footer>
  <div class="overlay">I'm overlay</div>
</div>
/* Fonts */
@import url("https://fonts.googleapis.com/css2?family=Open+Sans:wght@300;400;500;600;700;800&display=swap");

/* Resets */
*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

/* Base Style */
body {
  color: white;
  font-family: "Open Sans", sans-serif;
  font-size: 1.5rem;
}

.parent > * {
  padding: 1rem;
}

header {
  background-color: #251947;
  border: 4px solid #6f35f1;
}

.left-side {
  background-color: #414819;
  border: 4px solid #859433;
}

main {
  background-color: #461947;
  border: 4px solid #923394;
}

.right-side {
  background-color: #1b4b40;
  border: 4px solid #369680;
}

footer {
  background-color: #251947;
  border: 4px solid #6f35f1;
}

.overlay {
  background-color: rgba(0, 0, 0, 0.75);
  border: 4px solid #f09329;
}

/* Mobile Styles */
.parent {
  display: grid;
  grid-template-areas:
    "head"
    "left"
    "main"
    "right"
    "foot";
  min-height: 100vh;
}

.parent > header,
footer {
  display: flex;
  align-items: center;
}

header {
  grid-area: head;
}

.left-side {
  grid-area: left;
}

main {
  grid-area: main;
}

.right-side {
  grid-area: right;
}

footer {
  grid-area: foot;
}

.overlay {
  display: flex;
  align-items: center;
  justify-content: center;
  grid-area: left-start / left-start / right-end / main-end;
}

/* Tablet styles */
@media screen and (min-width: 500px) {
  .parent {
    grid-template-columns: 0.5fr 1fr;
    grid-template-rows: 100px 1fr 1fr 100px;
    grid-template-areas:
      "head head"
      "left main"
      "right main"
      "foot foot";
  }
}

/* laptop and desktop styles */
@media screen and (min-width: 960px) {
  .parent {
    grid-template-columns: 200px 1fr 200px;
    grid-template-areas:
      "head head head"
      "left main right"
      "left main right"
      "foot foot foot";
  }
  .overlay {
    grid-area: left-start / left-start / right-end / right-end;
  }
}

External CSS

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External JavaScript

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