body{
  margin: 0;
  padding: 0;
  height:100vh;
  overflow: hidden;
  width:100%;
  display: flex;
  background: #222;
  align-items: center;
  justify-content: center;
}

#emoji-btn {
  font-size: 3rem;
  filter: grayscale(1);
  transition: .1s;
  border: none;
  cursor: pointer;
}

#emoji-btn:hover {
  transform: scale(1.23);
  filter: grayscale(0);
}

// Get emojis from https://emojipedia.org/

const btn = document.getElementById("emoji-btn");
const emojis = [ 
    "😆",  "😅",  "🤣",  "😂",  "😀",  "🤑",  "🤨",  "🙂",
    "😊",  "😗",  "😛",  "😏",  "🤥",  "😴",  "🥺", "😧",
    "🤗",  "🤩",  "😎",  "🥳",  "😍",  "😱",  "🤓", "😷",
    "🥴",  "😳",  "🤯",  "🤫",  "🤑",  "😪",  "😴", "😵"
];

btn.addEventListener("mouseover", () => {
  btn.innerText = emojis[Math.floor(Math.random() * emojis.length)];
});