/* set the drumset at the bottom of the page */
#drumset {
  position: absolute;
  bottom: 0;
  left: 0;
  width: 100%;
  text-align: center;
}

/* make gray drums rounded with a darker border */
.drum {
  width: 20vmin;
  height: 20vmin;
  background: #ccc;
  box-sizing: border-box;
  border: 1vmin solid #333;
  border-radius: 50%;
  position: relative;
  display: inline-block;
  margin-bottom: 5vmin;
}

/* make each drum of its respective color (remember 2-3-0-1) */
#drum-0 {
  box-shadow: inset 0 0 0 2vmin blue;
  top: -5vmin;
}

#drum-1 {
  box-shadow: inset 0 0 0 2vmin green;
}

#drum-2 {
  box-shadow: inset 0 0 0 2vmin red;
}

#drum-3 {
  box-shadow: inset 0 0 0 2vmin yellow;
  top: -5vmin;
}