* {
  margin: 0;
  padding: 0;
  border: 0 none;
  box-sizing: border-box;
  user-select: none;
}

html, body {
  font: 1em / 1.5 'Overpass Mono', monospace;
  font-weight: 400;
  text-transform: uppercase;
  background-color: hsl(0, 0%, 4%);
  color: white;
}

header {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  height: 5rem;
  line-height: 1;
  border-top: 1px solid hsl(0, 0%, 8%);
  font-weight: 600;
  letter-spacing: 0.1em;
  text-align: center;
  background-color: black;
  color: hsl(0, 0%, 90%);
  
  &:before,
  &:after {
    content: '//';
    padding: 0 1em;
    opacity: 0.5;
  }
}

#BPM {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 200vv;
  height: 100vh;
  padding: 1rem 1rem 6rem 1rem;
  font-size: 8rem;
  cursor: pointer;
  
  .helper {
    display: block;
    flex: 0 1 9rem;
    width: 29rem;
    padding: 1rem 0rem 0.75rem 1rem;
    border: 2px solid currentcolor;
    font-size: 2rem;
    letter-spacing: 1em;
    line-height: 2;
    text-align: center;
  }
}