* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: monospace, serif;
}

.container {
  max-width: 900px;
  margin: 10px auto;
  padding: 5px;
}

.octave-keys {
  display: flex;
  gap: 1rem;
}

.octave-keys input {
  min-width: 130px;
  padding: 13px;
  cursor: pointer;
  border: none;
  outline: none;
  border-radius: 5px;
  color: #fff;
  font-size: 1.1rem;
  font-weight: bolder;
}

.octave-keys .octave-up {
  background-color: rgb(38, 177, 38);
}
.octave-keys .octave-down {
  background-color: rgb(198, 88, 88);
}
.current-octave {
  margin: 14px 0;
}
.music-keys {
  min-height: 300px;
  border: 2px solid #000;
  margin: 40px 0;
  border-radius: 5px;
  display: flex;
  box-shadow: 0 0 50px rgba(0, 0, 0, 0.3);
}
.key-container {
  display: flex;
  flex: 1;
  position: relative;
}
.key-container .key {
  width: 100%;
  height: 300px;
  border: 1px solid #000;
  border-radius: 5px;
  box-shadow: 0 0 15px rgba(0, 0, 0, 0.3);
}
.key.key-pressed {
  box-shadow: none;
}

.key-container .key.black {
  height: 150px;
  background-color: #000;
  position: absolute;
  left: 50%;
  border-right: 1px solid rgb(255, 255, 255);
  border-left: 1px solid #fff;
  z-index: 2;
}