Key Sequence Detection

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Key Sequence Detection</title>

  <link rel="stylesheet" href="./styles.css"/>
</head>
<body>
  <h1 class="title">Key Sequence<br>Detection</h1>

  <p class="instruction">Enter the word 'donut'</p>

  <iframe id="gif" src="https://giphy.com/embed/l41lZxzroU33typuU" width="480" height="321"></iframe>
  <p><a href="https://giphy.com/gifs/full-house-michelle-tanner-you-got-it-dude-l41lZxzroU33typuU"></a></p>

  <script src="./scripts.js"></script>
</body>
</html>

@import url('https://fonts.googleapis.com/css?family=BioRhyme+Expanded:800|Raleway');

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  height: 100vh;
  display: flex;
  justify-content: space-evenly;
  align-items: center;
  flex-direction: column;
  background: linear-gradient(to right, #396afc, #2948ff);
}

.title {
  color: #FFCC29;
  font-family: 'BioRhyme Expanded', serif;
  font-size: 40px;
  text-align: center;
  text-shadow: 2px 2px 2px rgba(0, 0, 0, 0.2);
}

.instruction {
  font-family: 'Raleway', sans-serif;
  font-size: 20px;
}

#gif {
  display: none;
  border: none;
}

#gif.show {
  display: block;
  animation: bounceDownIn 0.35s ease-in-out both;
}

@keyframes bounceDownIn {
  0%    { opacity: 0; transform: translateY(-2000px); }
  60%   { opacity: 1; transform: translateY(30px); }
  80%   { transform: translateY(-10px); }
  100%  { transform: translateY(0); }
}

@media screen and (max-width: 500px) {
  .title { font-size: 30px; }
  #gif { height: 50vh; }
}

const gif = document.querySelector('iframe'),
      sequenceToMatch = 'donut';

let inputSequence = [];

function detectKeySequence(e) {
  inputSequence.push(e.key);
  inputSequence.splice(-sequenceToMatch.length - 1, inputSequence.length - sequenceToMatch.length);

  let isMatch = inputSequence.join('') === sequenceToMatch;
  isMatch && gif.classList.add('show');
}

window.addEventListener('keyup', detectKeySequence);