:root {
    --primary-color: #4a6fa5;
    --secondary-color: #166088;
    --accent-color: #4fc3f7;
    --light-color: #f8f9fa;
    --dark-color: #343a40;
    --transition-speed: 0.3s;
    --piano-black: #222;
    --piano-white: #fff;
    --piano-active: var(--accent-color);
    --piano-shadow: rgba(0, 0, 0, 0.15);
}

/* Modo oscuro */
.dark-mode {
    --primary-color: #4a90e2;
    --secondary-color: #2a75bb;
    --accent-color: #3399ff;
    --light-color: #121212;
    --dark-color: #e0e0e0;
    --piano-black: #ddd;
    --piano-white: #222;
    --piano-active: #3399ff;
    --piano-shadow: rgba(255, 255, 255, 0.1);
}

/* ===== Estilos Generales ===== */
body {
    font-family: 'Roboto', sans-serif;
    color: var(--dark-color);
    background-color: var(--light-color);
    transition: background-color var(--transition-speed), color var(--transition-speed);
}

.library-container {
    max-width: 1100px;
    margin: 3rem auto;
    padding: 2rem;
    background: var(--light-color);
    border-radius: 16px;
    box-shadow: 0 8px 25px var(--piano-shadow);
    transition: all var(--transition-speed);
}

/* ===== Piano Styles Modern ===== */
.piano-keys {
    position: relative;
    width: 100%;
    max-width: 700px;
    margin: 2rem auto;
    aspect-ratio: 3/1;
    display: flex;
    border-radius: 10px;
    overflow: hidden;
    box-shadow: 0 6px 18px var(--piano-shadow);
    background: linear-gradient(180deg, #fdfdfd, #eaeaea);
    transition: background var(--transition-speed);
}

.dark-mode .piano-keys {
    background: linear-gradient(180deg, #2a2a2a, #1a1a1a);
}

.piano-key {
    position: relative;
    flex: 1;
    border: 1px solid #ccc;
    box-sizing: border-box;
    transition: all var(--transition-speed) ease;
}

.dark-mode .piano-key {
    border-color: #555;
}

.white-key {
    background: var(--piano-white);
    z-index: 1;
    border-right: 1px solid #bbb;
}

.dark-mode .white-key {
    background: var(--piano-black);
    border-right: 1px solid #444;
}

.black-key {
    position: absolute;
    width: 60%;
    height: 60%;
    background: var(--piano-black);
    z-index: 2;
    border-radius: 0 0 5px 5px;
    box-shadow: inset -2px -2px 5px rgba(0, 0, 0, 0.4);
    transform-origin: bottom;
    transition: transform var(--transition-speed) ease, background var(--transition-speed) ease;
}

.dark-mode .black-key {
    background: var(--piano-white);
    box-shadow: inset -2px -2px 5px rgba(255, 255, 255, 0.2);
}

/* Posicionamiento teclas negras (patrón 2-3) */
.black-key[data-note^="C#"] { left: calc(100% / 14 * 1.65); }
.black-key[data-note^="D#"] { left: calc(100% / 14 * 2.65); }
.black-key[data-note^="F#"] { left: calc(100% / 14 * 5.65); }
.black-key[data-note^="G#"] { left: calc(100% / 14 * 6.65); }
.black-key[data-note^="A#"] { left: calc(100% / 14 * 7.65); }

/* Teclas activas */
.piano-key.active {
    background-color: var(--piano-active);
    box-shadow: 0 0 15px var(--piano-active);
}

.piano-key.active.black-key {
    background-color: var(--secondary-color);
    box-shadow: 0 0 10px var(--secondary-color);
    transform: scaleY(0.95);
}

/* Finger Label */
.finger {
    position: absolute;
    bottom: 5px;
    width: 100%;
    text-align: center;
    font-weight: bold;
    font-size: 0.85rem;
    color: var(--light-color);
}

.dark-mode .finger {
    color: var(--dark-color);
}

/* ===== Tarjetas de Instrumentos ===== */
.instrument-card {
    border: none;
    border-radius: 14px;
    box-shadow: 0 6px 18px var(--piano-shadow);
    background: var(--light-color);
    transition: transform var(--transition-speed) ease;
}

.dark-mode .instrument-card {
    background: #1a1a1a;
    box-shadow: 0 6px 18px rgba(255, 255, 255, 0.1);
}

.instrument-card:hover {
    transform: translateY(-8px);
}

/* ===== Botones Modernos ===== */
.btn-primary {
    background-color: var(--primary-color);
    color: white;
    border-radius: 50px;
    padding: 0.75rem 2rem;
    box-shadow: 0 4px 8px var(--piano-shadow);
    transition: all var(--transition-speed);
}

.btn-primary:hover {
    background-color: var(--secondary-color);
    transform: translateY(-2px);
}

/* ===== Animación Fade In ===== */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(15px); }
    to { opacity: 1; transform: translateY(0); }
}

.library-container {
    animation: fadeIn 0.6s ease-out;
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
    .piano-keys {
        aspect-ratio: 4/1;
    }

    .black-key {
        height: 55%;
    }

    .library-container {
        padding: 1rem;
    }

    .btn-primary {
        padding: 0.5rem 1.5rem;
    }
}