<body>
  <div class="codepen">
    <header class="pen">
      <div class="pen__details">
        <h1>Some Amazing Pen Name</h1>
        <p class="pen__author">Marco Kühbauch</p>
      </div>
      <button class="button button--dirty">☁️ Save</button>
      <button class="button">️️☁️ Save As Private</button>
      <button class="button">⚙ Settings</button>
      <button class="button">👀 Change View</button>
      <img src="https://s3-us-west-2.amazonaws.com/s.cdpn.io/28831/profile/profile-80.jpg?1" alt="Wes Bos" height="44">
    </header>
    <section class="code">
      <div class="editor">
        <header class="editor__header">
          <button class="button button--small editor__settings">⚙</button>
          <h3 class="editor__heading">HTML</h3>
          <button class="button button--small editor__settings">⌄</button>
        </header>
        <div class="editor__code">
          <div class="editor__gutter">
            <span class="editor__number">1</span>
          </div>

          <textarea class="editor__input"><p>Oh Hey There!</p></textarea>
        </div>
      </div>
      <div class="editor">
        <header class="editor__header">
          <button class="button button--small editor__settings">⚙</button>
          <h3 class="editor__heading">CSS</h3>
          <button class="button button--small editor__settings">⌄</button>
        </header>
        <div class="editor__code">
          <div class="editor__gutter">
            <span class="editor__number">1</span>
            <span class="editor__number">2</span>
            <span class="editor__number">3</span>
          </div>

          <textarea class="editor__input">.codepen {
  is: cool;
}
          </textarea>
        </div>

      </div>
      <div class="editor">
        <header class="editor__header">
          <button class="button button--small editor__settings">⚙</button>
          <h3 class="editor__heading">JS</h3>
          <button class="button button--small editor__settings">⌄</button>
        </header>
        <div class="editor__code">
          <div class="editor__gutter">
            <span class="editor__number">1</span>
          </div>
          <textarea class="editor__input">const wes = 'coolest';</textarea>
        </div>

      </div>
    </section>
    <section class="preview">
      <iframe src="https://marcokuehbauch.com" frameborder="0"></iframe>
    </section>
    <footer class="settings">
      <button class="button button--small button--black">Console</button>
      <button class="button button--small button--black">Assets</button>
      <button class="button button--small button--black">⌘</button>
    </footer>
  </div>
</body>
:root {
  --grey: #343436;
}

.codepen {
  color: white;
  display: grid;
  grid-template-rows: auto 1fr 1fr auto;
  height: 100vh;
}

.codepen>* {
  border: 1px solid black;
}

/* Editor */
.code {
  background: #1b2b34;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
}

.editor {
  display: grid;
  grid-template-rows: auto 1fr;
}

.editor__header {
  display: grid;
  grid-template-columns: auto 1fr auto;
  align-items: center;
  padding: 5px;
  grid-gap: 5px;
  background: rgb(0, 0, 0, .1);
}

.editor__code {
  display: grid;
  grid-template-columns: auto 1fr;
}

.editor__number {
  display: block;
  padding: 0 10px;
}

.editor__input {
  resize: none;
  background: none;
  border: 0;
  color: grey;
  font-size: 16px;
  line-height: 19px;
}

.settings {
  padding: 5px;
  background: black;
  border-top: 1px solid grey;
}

/* Pen Header */

.pen {
  align-items: center;
  background: black;
  border-bottom: 5px solid var(--grey);
  color: white;
  display: grid;
  grid-template-columns: 1fr;
  grid-auto-flow: column;
  grid-gap: 10px;
}

.preview {
  display: grid;
}

/* Buttons */

.button {
  background: var(--grey);
  border: 0;
  color: white;
  padding: 10px;
  border-radius: 5px;
  font-size: 15px;
  position: relative;
}

.button--small {
  font-size: 12px;
  padding: 4px;
}

.button--dirty:before {
  background: #ffc600;
  display: block;
  content: "";
  height: 2px;
  width: calc(100% - 6px);
  position: absolute;
  left: 3px;
  top: 3px;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.