styles.css

body {
  text-align: center;
  background-color: #011F3F;
 background-color: #000;
}

#level-title {
  font-family: 'Press Start 2P', cursive;
  font-size: 3rem;
  margin:  5%;
  color: #FEF2BF;
}

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

}

.btn {
  margin: 25px;
  display: inline-block;
  height: 200px;
  width: 200px;
  border: 10px solid black;
  border-radius: 50%;
}

.game-over {
  background-color: red;
  opacity: 0.8;
}

.red {
border:2px solid red;
background-color: none;
box-shadow: inset 0px 0px 10px 2px rgba(117,182,255,0.5),
                      0px 0px 40px 2px rgba(255,0,0,1);
}

.green {
  border:2px solid green;
  background-color: none;
  box-shadow: inset 0px 0px 10px 2px rgba(117,182,255,0.5),
                      0px 0px 60px 2px rgba(0,128,0,1);
  /* animation: glow 1s alternate infinite; */

}

.blue {
  border:2px solid blue;
  background-color: none;
  box-shadow: inset 0px 0px 10px 2px rgba(117,182,255,0.5),
  0px 0px 40px 2px rgba(0,0,255,1);
}

.yellow {
  border:2px solid yellow;
  background-color: none;
  box-shadow: inset 0px 0px 10px 2px rgba(117,182,255,0.5),
  0px 0px 40px 2px rgba(255,255,0,1);
}

.pressed {
  /* box-shadow: 0 0 20px white;
  background-color: grey; */
  animation: glow 1s alternate infinite;

}

@keyframes glow {
  0% {
    background: rgba(255,255,255,0.7);
    box-shadow: inset 0px 0px 10px 2px rgba(117,182,255,0.5),
                      0px 0px 40px 2px rgba(105,135,255,1);
  }
  100% {
    background: rgba(255,255,255,0.2);
    box-shadow: inset 0px 0px 10px 2px rgba(117,182,255,0.5),
                      0px 0px 30px 2px rgba(105,135,255,0.3);
  }
}