piano-midi-monitor/style.css

html {
  height: 100%;
  width: 100%;
}

body {
  margin: 0;
  display: flex;
  justify-content: space-between;
  align-items: center;
  width: 100%;
  height: 100%;
}

svg {
  fill: currentColor;
}

.natural {
  height: 100%;
  box-sizing: border-box;
  background-image: url('./natural.png');
  background-color: black;
  z-index: 0;
}

.accidental {
  height: calc(41 / 64 * 100%);
  box-sizing: border-box;
  background-image: url('./accidental.png');
  z-index: 2;
}

.key > * {
  width: 100%;
  height: 100%;
  opacity: 0;
  background-color: lime;
  border-radius: 0 0 1px 1px;
  background-clip: content-box;
  box-sizing: border-box;

}

.natural.key > * {
  padding: 2px 0 0 1px;
  mix-blend-mode: multiply;
}

.accidental.key > * {
  padding: 2px 0 1px 1px;
  mix-blend-mode: hard-light;
}

.natural.key.pressed {
  z-index: 1;
}

.accidental.key.pressed {
  z-index: 3;
}

.natural.key.pressed > * {
  opacity: 0.85;
}

.accidental.key.pressed > * {
  opacity: 0.5;
}

#pedals {
  display: flex;
  justify-content: space-between;

  align-items: center;
  width: 0;
  flex: auto;
  padding: 0 1rem;
  box-sizing: border-box;
  background-color: black;
  color: white;
  height: 100%;
}