* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background-color: #f9fafb;
    color: #111827;
    line-height: 1.65;
}

header {
    background-color: #1e40af;
    color: white;
    text-align: center;
    padding: 3.5rem 1rem 4rem;
}

header h1 {
    font-size: 2.6rem;
    font-weight: 700;
}

.contenedor {
    max-width: 820px;
    margin: 0 auto;
    padding: 0 1.2rem;
}

.tarjeta-presentacion {
    background: white;
    border-radius: 16px;
    box-shadow: 0 6px 24px rgba(0,0,0,0.08);
    padding: 2.2rem 1.8rem;
    margin: -3.5rem auto 3rem;
}

.tarjeta-presentacion h2 {
    color: #1e40af;
    font-size: 1.65rem;
    margin-bottom: 1.3rem;
}

.tarjeta-presentacion p {
    margin-bottom: 1.4rem;
    font-size: 1.08rem;
}

.info-autor {
    margin: 2.2rem 0;
    padding: 1.6rem;
    background: #f0f7ff;
    border-radius: 12px;
    border-left: 5px solid #3b82f6;
}

.info-autor h3 {
    color: #1d4ed8;
    margin-bottom: 0.9rem;
    font-size: 1.35rem;
}

.imagen-portada {
    display: block;
    max-width: 100%;
    height: auto;
    border-radius: 12px;
    margin: 2.2rem auto;
    box-shadow: 0 8px 24px rgba(0,0,0,0.1);
}

.indice {
    background: white;
    border-radius: 16px;
    box-shadow: 0 6px 24px rgba(0,0,0,0.08);
    padding: 2rem;
    margin-bottom: 3rem;
}

.indice h2 {
    text-align: center;
    color: #1e40af;
    margin-bottom: 1.6rem;
    font-size: 1.8rem;
}

.indice ul {
    list-style: none;
}

.indice li {
    margin: 1.1rem 0;
}

.indice a {
    display: block;
    padding: 1.1rem 1.6rem;
    background: #eff6ff;
    color: #1d4ed8;
    text-decoration: none;
    border-radius: 10px;
    font-weight: 600;
    font-size: 1.05rem;
    border: 1px solid #bfdbfe;
    transition: all 0.2s;
}

.indice a:hover {
    background: #dbeafe;
    transform: translateY(-2px);
}

.centro {
    text-align: center;
    margin: 3rem 0 4rem;
}

.boton-principal {
    display: inline-block;
    background: #2563eb;
    color: white;
    padding: 1.1rem 2.6rem;
    font-size: 1.22rem;
    font-weight: 600;
    text-decoration: none;
    border-radius: 999px;
    box-shadow: 0 5px 15px rgba(37,99,235,0.25);
    transition: all 0.25s;
}

.boton-principal:hover {
    background: #1d4ed8;
    transform: translateY(-3px);
    box-shadow: 0 10px 25px rgba(29,78,216,0.35);
}

.contacto {
    text-align: center;
    padding: 3.5rem 1rem;
    background: #f1f5f9;
}

.contacto h2 {
    color: #1e40af;
    margin-bottom: 1.2rem;
    font-size: 1.7rem;
}

.contacto p {
    font-size: 1.25rem;
}

footer {
    background: #111827;
    color: #9ca3af;
    text-align: center;
    padding: 2.2rem 1rem;
    font-size: 0.98rem;
}

/* ────────────────────────────────────────────────
   RESPONSIVE - CELULARES Y TABLETS
───────────────────────────────────────────────── */
@media (max-width: 680px) {
    header {
        padding: 2.8rem 1rem 3.5rem;
    }
    header h1 {
        font-size: 2.1rem;
    }
    .tarjeta-presentacion {
        margin: -2.5rem 0.8rem 2.5rem;
        padding: 1.8rem 1.4rem;
    }
    .tarjeta-presentacion h2 {
        font-size: 1.45rem;
    }
    .tarjeta-presentacion p {
        font-size: 1.02rem;
    }
    .info-autor {
        padding: 1.4rem;
    }
    .indice {
        padding: 1.6rem;
    }
    .indice h2 {
        font-size: 1.6rem;
    }
    .indice a {
        padding: 1rem 1.3rem;
        font-size: 1.02rem;
    }
    .boton-principal {
        padding: 1rem 2.2rem;
        font-size: 1.15rem;
    }
    .contacto {
        padding: 3rem 1rem;
    }
    .contacto h2 {
        font-size: 1.55rem;
    }
    .contacto p {
        font-size: 1.18rem;
    }
}

@media (max-width: 480px) {
    header h1 {
        font-size: 1.9rem;
    }
    .tarjeta-presentacion {
        padding: 1.6rem 1.2rem;
    }
    .boton-principal {
        width: 100%;
        max-width: 320px;
    }
}
















/* Estenedor principal */
.menu-desplegable {
    position: absolute;
    top: 20px;
    left: 20px;
    z-index: 9999;
}

/* Botón principal */
.boton-menu {
    background-color: #1e40af;
    color: white;
    padding: 12px 24px;
    border: none;
    border-radius: 12px;
    cursor: pointer;
    font-weight: bold;
    box-shadow: 0 4px 12px rgba(0,0,0,0.15);
}

/* Caja del menú (oculta al inicio) */
.enlaces-menu {
    display: none;
    position: absolute;
    background-color: white;
    min-width: 260px;
    box-shadow: 0 10px 25px rgba(0,0,0,0.2);
    border-radius: 12px;
    margin-top: 12px;
    padding: 8px;
    overflow: hidden;
}

.mostrar { display: block; }

/* Elementos del tema */
.item-tema {
    padding: 15px;
    border-radius: 8px;
    transition: background 0.3s;
}

.titulo-tema {
    color: #1e40af;
    text-decoration: none;
    font-weight: 700;
    display: block;
    font-size: 1rem;
}

/* RESUMEN OCULTO: Solo aparece al poner el mouse */
.resumen-oculto {
    max-height: 0;
    opacity: 0;
    overflow: hidden;
    transition: all 0.4s ease;
    font-size: 0.9rem;
    color: #4b5563;
    margin-top: 0;
    line-height: 1.4;
}

/* EFECTO HOVER: Muestra el resumen y cambia fondo */
.item-tema:hover {
    background-color: #f0f7ff;
}

.item-tema:hover .resumen-oculto {
    max-height: 100px; /* Permite que el texto baje */
    opacity: 1;
    margin-top: 8px;
}