body {
  text-align: center;
  background-image: url("images/background.jpg");
  background-repeat: no-repeat;
  background-size: cover;
}

#level-title {
  font-family: 'Monoton', cursive;
  font-size: 3.3rem;
  margin: 2.1%;
  font-weight: 100;
  color: black;
}

.container {
  display: block;
  width: 50%;
  margin: auto;
}

.btn {
  margin: 25px;
  display: inline-block;
  height: 200px;
  width: 200px;
  border: 10px solid grey;
  border-radius: 100%;
}

.game-over {
  background-image: url("https://pbs.twimg.com/media/Ds8kxCGU0AI1Hu5.jpg:large");
  background-repeat: no-repeat;
  background-size: 1000px;
  background-position: 640px;
  opacity: 0.8;
}

.red {
  background-image: url("https://www.transparentpng.com/thumb/iron-man/p2VriY-iron-man-free-download-transparent.png");
  background-size: cover;
}

.green {
  background-image: url("https://www.picng.com/upload/hulk/png_hulk_75126.png");
  background-repeat: no-repeat;
  background-size: cover;
  background-position: top 0px right 0px;
}

.blue {
  background-image: url("https://clipartix.com/wp-content/uploads/2018/03/thor-clipart-2018-17.png");
  background-repeat: no-repeat;
  background-size: 450px;
  background-position: top -20px left -60px;
}

.yellow {
  background-image: url("https://www.seekpng.com/png/full/3-35972_captain-america-png-image-hawkeye-captain-america-comic.png");
  background-repeat: no-repeat;
  background-size: 300px;
  background-position: top 10px right 0px;
}

.pressed {
  box-shadow: 0 0 20px grey;
  background-color: grey;
}

footer {
  float: left;
  font-family: 'Nosifer', cursive;
  font-weight: 100;
  transform: rotate(-90deg);
  position: relative;
  bottom: 125px;
  left: -100px;
  color: rgb(97, 97, 97);
}