#keyboard {
  cursor: pointer;
  user-select: none;
}

#keyboard ul {
  margin: 0 auto;
  padding: 0;
  list-style: none;
  perspective: 1400px;
}

#keyboard ul li {
  float: left;
  width: 4.236067987318243rem; /* key width */
  height: 6.8541019874318065rem; /* key height */
  display: flex;
  align-items: flex-end;
  font-family: "Helvetica", sans-serif;
  font-size: 0.9rem;
  text-transform: uppercase;
  padding-left: 0.2rem;
  padding-bottom: 0.1rem;
  margin-right: 0.2rem;
  border-radius: 0 0 1rem 1rem; /* smooth rounded bottom edges */
  box-sizing: border-box;
  background: linear-gradient(to top right, #fdfdfd, #d1d1d1);
  color: #555;
  text-shadow: 1px 1px 1px #ffffff;
  border: 0.1rem solid #bfbfbf;
  border-bottom: 0.3rem solid #a7a7a7;
  box-shadow: 0 6px 6px -4px #000; /* refined shadow */
}

#keyboard ul li.active {
  background: linear-gradient(to top right, #e0e0e0, #ffffff);
  box-shadow: 0 3px 3px -2px #000; /* lighter shadow when active */
}

#keyboard ul li.accidental {
  position: relative;
  margin-left: -1.61803399rem;
  margin-right: -3.7360679836591215rem;
  height: 4.236067987318243rem; /* shorter key for accidentals */
  background: linear-gradient(to top right, #303030, #505050);
  color: #ffffff;
  text-shadow: 0 1px 0 #000000;
  border-top: 0.1rem solid #333;
  border-left: 0.2rem solid #111;
  border-right: 0.2rem solid #111;
  border-bottom: 0.3rem solid #000;
  box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.6),
    0 -1px 5px rgba(255, 255, 255, 0.1); /* more refined shadows */
  border-radius: 0 0 0.5rem 0.5rem; /* rounded bottom for accidentals */
}

#keyboard ul li.accidental.active {
  background: linear-gradient(to top right, #383838, #585858);
  box-shadow: 0 2px 3px -1px rgba(0, 0, 0, 0.6); /* less intense shadow for active state */
}

#keyboard ul li:last-child {
  margin-right: 0;
}