body {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  background-color: #e3f2fd;
  color: #ffff;
}

.container {
  width: 780px;
  background-color: black;
  border-radius: 2rem;
  padding: 3rem;
}
.container header {
  color: #b2b2b2;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
header h2 {
  font-size: 1.6rem;
}

header .column {
  display: flex;
  align-items: center;
}

header .column span {
  font-weight: 500;
  margin-right: 15px;
  font-size: 1.19rem;
}
.volume-slider input {
  accent-color: #ffff;
}
.keys-check input {
  width: 60px;
  height: 30px;
  appearance: none;
  border-radius: 3rem;
  background-color: #4b4b4b;
  cursor: pointer;
  position: relative;
}
.keys-check input::before {
  content: "";
  height: 20px;
  width: 20px;
  background-color: #8c8c8c;
  position: absolute;
  top: 50%;
  left: 0.3rem;
  border-radius: inherit;
  transform: translateY(-50%);
  transition: all 0.3s ease;
}
.keys-check input:checked::before {
  left: 2.1rem;
  background-color: #fff;
}
.piano-keys {
  display: flex;
  margin-top: 40px;
}
.piano-keys .key {
  cursor: pointer;
  list-style: none;
  color: #a2a2a2;
  position: relative;
  text-transform: uppercase;
}
.piano-keys .white {
  width: 70px;
  height: 230px;
  border: 1px solid black;
  background: linear-gradient(#fff 96%, #eee 4%);
  border-radius: 8px;
}
.piano-keys .black {
  width: 44px;
  height: 140px;
  z-index: 2;
  margin: 0 -22px 0 -22px;
  background: linear-gradient(#000 0%, #333 54%, #000 55%, #333 90%);
  border-radius: 0 0 5px 5px;
}
.piano-keys span {
  position: absolute;
  bottom: 20px;
  width: 100%;
  text-align: center;
  font-size: 1.3rem;
}
.piano-keys .white.active {
  box-shadow: inset -5px 5px 20px rgba(0, 0, 0, 0.2);
  background: linear-gradient(to bottom #fff 0%, #eee 100%);
}
.piano-keys .black.active {
  box-shadow: -5px 5px 5px rgba(0, 0, 0, 0.3);
  background: linear-gradient(#000 0%, #333 42%, #000 46%, #333 90%);
}
.piano-keys .key.hide span {
  display: none;
}

.container header .light-dial {
  margin-left: 20px; 
  display: flex; 
  align-items: center;
}

.light-dial .dial-indicator {
  width: 30px; 
  height: 30px;
  background-color: #333; 
  border-radius: 50%;
  opacity: 0.5; 
  transition: background-color 0.1s ease-out, opacity 0.1s ease-out;
}

.light-dial .dial-indicator.active {
  background-color: #00bfff; 
  box-shadow: 0 0 15px #00bfff, 0 0 25px #00bfff; 
  opacity: 1;
}