<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=1" />

    <title>Calculator</title>

    <link rel="stylesheet" href="./index.css" />
  </head>
  <body>
    <h1>Calculator</h1>

    <p>With an empty display.</p>

    <div class="calculator">
      <div class="calculator__display">
        <div class="display">
          <div class="display__line1"></div>
          <div class="display__line2"></div>
