style.css

html,
body {
  height: 100%;
  margin: 0;
}
body {
  font-family: "Press Start 2P", cursive;
  cursor: pointer;
}
.container {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100%;
}
#score {
  position: absolute;
  top: 30px;
  right: 30px;
  font-size: 2em;
  font-weight: 900;
}
#introduction {
  width: 200px;
  height: 150px;
  position: absolute;
  font-weight: 600;
  font-size: 0.8em;
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  text-align: center;
  transition: opacity 2s;
}
#restart {
  width: 120px;
  height: 120px;
  position: absolute;
  border-radius: 50%;
  color: white;
  background-color: red;
  border: none;
  font-weight: 700;
  font-size: 1.2em;
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  display: none;
  cursor: pointer;
}
#perfect {
  position: absolute;
  opacity: 0;
  transition: opacity 2s;
}
#youtube,
#youtube-card {
  display: none;
}
@media (min-height: 425px) {
  #youtube {
    z-index: 2;
    display: block;
    width: 100px;
    height: 70px;
    position: absolute;
    bottom: 20px;
    left: 20px;
    background: red;
    border-radius: 50% / 11%;
    transform: scale(0.8);
    transition: transform 0.5s;
  }
  #youtube:hover,
  #youtube:focus {
    transform: scale(0.9);
  }
  #youtube::before {
    content: "";
    display: block;
    position: absolute;
    top: 7.5%;
    left: -6%;
    width: 112%;
    height: 85%;
    background: red;
    border-radius: 9% / 50%;
  }
  #youtube::after {
    content: "";
    display: block;
    position: absolute;
    top: 20px;
    left: 40px;
    width: 45px;
    height: 30px;
    border: 15px solid transparent;
    box-sizing: border-box;
    border-left: 30px solid white;
  }
  #youtube span {
    font-size: 0;
    position: absolute;
    width: 0;
    height: 0;
    overflow: hidden;
  }
  #youtube:hover + #youtube-card {
    display: block;
    position: absolute;
    bottom: 12px;
    left: 10px;
    padding: 25px 25px 25px 130px;
    width: 300px;
    background-color: white;
  }
}