/* ============================================
   VARIABLES Y ESTILOS GLOBALES
   ============================================ */

:root {
    /* Colores */
    --color-primary: #00a8ff;
    --color-primary-dark: #0088cc;
    --color-secondary: #b0b0b0;
    --color-success: #28a745;
    --color-danger: #ff6b6b;
    --color-light: #2a2a2a;
    --color-dark: #1a1a1a;
    --color-white: #e0e0e0;
    
    /* Colores para dark mode */
    --color-bg-dark: #0f0f0f;
    --color-bg-light: #1f1f1f;
    --color-bg-lighter: #2a2a2a;
    --color-bg-darker: #0a0a0a;
    --color-text-primary: #e0e0e0;
    --color-text-secondary: #b0b0b0;
    
    /* Tipografía */
    --font-primary: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    
    /* Espacios */
    --spacing-unit: 8px;
    --spacing-small: calc(var(--spacing-unit) * 1);
    --spacing-medium: calc(var(--spacing-unit) * 2);
    --spacing-large: calc(var(--spacing-unit) * 3);
    --spacing-xl: calc(var(--spacing-unit) * 4);
    --spacing-2xl: calc(var(--spacing-unit) * 5);
    
    /* Sombras oscuras */
    --shadow-small: 0 2px 4px rgba(0, 0, 0, 0.5);
    --shadow-medium: 0 4px 8px rgba(0, 0, 0, 0.6);
    --shadow-large: 0 8px 16px rgba(0, 0, 0, 0.7);
    
    /* Bordes */
    --radius-small: 4px;
    --radius-medium: 8px;
    --radius-large: 12px;
}

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

/* Estilos base */
html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-primary);
    line-height: 1.6;
    color: var(--color-text-primary);
    background-color: var(--color-bg-dark);
}

/* ============================================
   HEADER Y NAVEGACIÓN
   ============================================ */

.header {
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
    color: var(--color-white);
    padding: var(--spacing-xl) var(--spacing-medium);
    text-align: center;
    box-shadow: var(--shadow-large);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-content {
    max-width: 1200px;
    margin: 0 auto;
}

.header h1 {
    font-size: 1.8rem;
    margin-bottom: var(--spacing-small);
    font-weight: 700;
    letter-spacing: -0.5px;
}

.subtitle {
    font-size: 0.95rem;
    opacity: 0.95;
    font-weight: 300;
}

/* Barra de navegación */
.navbar {
    background-color: var(--color-bg-lighter);
    box-shadow: var(--shadow-small);
    position: sticky;
    top: 0;
    z-index: 99;
}

.nav-list {
    list-style: none;
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    max-width: 1200px;
    margin: 0 auto;
    gap: 0;
}

.nav-list li {
    flex: 1;
    max-width: 200px;
}

.nav-list a {
    display: block;
    padding: var(--spacing-medium) var(--spacing-small);
    text-decoration: none;
    color: var(--color-text-primary);
    font-weight: 500;
    text-align: center;
    transition: all 0.3s ease;
    border-bottom: 3px solid transparent;
    font-size: 0.9rem;
}

.nav-list a:hover {
    background-color: var(--color-bg-light);
    border-bottom-color: var(--color-primary);
    color: var(--color-primary);
}

/* ============================================
   CONTAINER Y SECCIONES
   ============================================ */

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-medium);
}

.section {
    background-color: var(--color-bg-lighter);
    padding: var(--spacing-xl);
    margin-bottom: var(--spacing-xl);
    border-radius: var(--radius-large);
    box-shadow: var(--shadow-medium);
}

.section-content {
    margin-bottom: var(--spacing-large);
}

.section h2 {
    font-size: 1.5rem;
    color: var(--color-primary);
    margin-bottom: var(--spacing-large);
    padding-bottom: var(--spacing-medium);
    border-bottom: 3px solid var(--color-bg-light);
}

.section h3 {
    font-size: 1.2rem;
    color: var(--color-text-primary);
    margin-bottom: var(--spacing-medium);
    margin-top: var(--spacing-large);
}

.section p {
    margin-bottom: var(--spacing-medium);
    line-height: 1.8;
    font-size: 1rem;
}

/* Sección de bienvenida */
.welcome {
    background: linear-gradient(135deg, rgba(0, 168, 255, 0.15) 0%, rgba(0, 168, 255, 0.08) 100%);
}

.intro-text {
    font-size: 1rem;
    line-height: 1.8;
    color: var(--color-text-primary);
}

.analogy {
    background-color: var(--color-bg-light);
    padding: var(--spacing-large);
    border-left: 4px solid var(--color-primary);
    border-radius: var(--radius-medium);
    margin: var(--spacing-large) 0;
    font-style: italic;
}

/* ============================================
   CONCEPTOS Y MÉTODOS
   ============================================ */

.concept {
    margin-bottom: var(--spacing-large);
    padding-bottom: var(--spacing-medium);
    border-bottom: 1px solid var(--color-light);
}

.concept:last-child {
    border-bottom: none;
}

.concept h3 {
    font-size: 1.1rem;
    margin-top: 0;
}

.method {
    background-color: var(--color-bg-light);
    padding: var(--spacing-large);
    margin: var(--spacing-medium) 0;
    border-radius: var(--radius-medium);
    border-left: 4px solid var(--color-primary);
}

.method h4 {
    font-size: 1rem;
    color: var(--color-primary);
    margin-bottom: var(--spacing-small);
}

.method p {
    margin-bottom: var(--spacing-medium);
}

.method code {
    background-color: var(--color-bg-darker);
    padding: 2px 6px;
    border-radius: var(--radius-small);
    font-family: 'Courier New', monospace;
    color: var(--color-primary);
}

/* Estructura CSS */
.structure {
    background: linear-gradient(to right, #1f1f1f, #2a2a2a);
    padding: var(--spacing-large);
    border-radius: var(--radius-medium);
    border: 2px solid var(--color-bg-light);
    margin: var(--spacing-large) 0;
    font-family: 'Courier New', monospace;
    font-size: 1rem;
}

.structure-part {
    display: block;
    line-height: 2;
}

.selector-label,
.property-label,
.value-label {
    display: inline-block;
    background-color: var(--color-bg-light);
    padding: 4px 8px;
    border-radius: var(--radius-small);
    font-size: 0.85rem;
    color: var(--color-text-secondary);
    margin-right: 8px;
    font-family: var(--font-primary);
}

.structure code {
    background-color: var(--color-bg-lighter);
    padding: 4px 8px;
    border-radius: var(--radius-small);
    color: var(--color-primary);
    font-weight: bold;
}

.colon,
.semicolon,
.brace {
    color: var(--color-primary);
    font-weight: bold;
    margin: 0 4px;
}

.explanation {
    margin-top: var(--spacing-medium);
    font-style: italic;
    color: var(--color-text-secondary);
}

/* ============================================
   BLOQUES DE CÓDIGO
   ============================================ */

.code-block {
    background-color: #1a1e27;
    color: #a0aec0;
    padding: var(--spacing-2xl);
    border-radius: var(--radius-medium);
    overflow-x: auto;
    margin: var(--spacing-medium) 0;
    font-size: 0.9rem;
    line-height: 1.8;
    border-left: 4px solid var(--color-primary);
}

.code-block pre {
    margin: 0;
    font-family: 'Courier New', monospace;
    word-wrap: break-word;
    white-space: pre-wrap;
}

/* ============================================
   TARJETAS DE SELECTORES Y PROPIEDADES
   ============================================ */

.selector-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-large);
    margin: var(--spacing-medium) 0;
}

.properties-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(400px, 1fr));
    gap: var(--spacing-large);
    margin: var(--spacing-medium) 0;
}

.selector-card,
.property-card {
    background-color: var(--color-bg-light);
    padding: var(--spacing-2xl);
    border-radius: var(--radius-large);
    border: 2px solid transparent;
    transition: all 0.3s ease;
    box-shadow: var(--shadow-small);
    display: flex;
    flex-direction: column;
}

.selector-card:hover,
.property-card:hover {
    border-color: var(--color-primary);
    box-shadow: var(--shadow-medium);
    transform: translateY(-4px);
}

.selector-card h3,
.property-card h3 {
    color: var(--color-primary);
    margin-top: 0;
    margin-bottom: var(--spacing-medium);
    font-size: 1.15rem;
    font-weight: 600;
}

.selector-card p,
.property-card p {
    font-size: 0.98rem;
    margin-bottom: 0;
    line-height: 1.7;
}

/* Tip Box */
.tip-box {
    background: linear-gradient(135deg, rgba(40, 167, 69, 0.15) 0%, rgba(40, 167, 69, 0.08) 100%);
    border-left: 4px solid var(--color-success);
    padding: var(--spacing-large);
    border-radius: var(--radius-medium);
    margin: var(--spacing-medium) 0;
}

.tip-box strong {
    color: var(--color-success);
}

.tip-box ul {
    margin: var(--spacing-medium) 0 0 var(--spacing-xl);
    list-style-position: inside;
}

.tip-box li {
    margin-bottom: var(--spacing-small);
}

/* ============================================
   BOX MODEL VISUALIZATION
   ============================================ */

.box-model-explanation {
    margin-top: var(--spacing-xl);
    padding: var(--spacing-large);
    background-color: var(--color-bg-light);
    border-radius: var(--radius-large);
}

.box-model-visual {
    margin: var(--spacing-large) auto;
    text-align: center;
}

.margin-demo {
    background-color: #334455;
    padding: 20px;
    border-radius: var(--radius-medium);
    margin: 15px auto;
    width: 90%;
    max-width: 350px;
}

.margin-demo > span {
    display: block;
    font-weight: bold;
    color: #88bbff;
    margin-bottom: 10px;
    font-size: 0.9rem;
}

.border-demo {
    background-color: #223344;
    padding: 20px;
    border: 3px solid #00a8ff;
    border-radius: var(--radius-medium);
}

.border-demo > span {
    display: block;
    font-weight: bold;
    color: #00a8ff;
    margin-bottom: 10px;
    font-size: 0.9rem;
}

.padding-demo {
    background-color: #334422;
    padding: 15px;
    border-radius: var(--radius-medium);
}

.padding-demo > span {
    display: block;
    font-weight: bold;
    color: #88ff88;
    margin-bottom: 10px;
    font-size: 0.9rem;
}

.content-demo {
    background-color: #444433;
    padding: 20px;
    border-radius: var(--radius-medium);
}

.content-demo span {
    display: block;
    font-weight: bold;
    color: #ffff88;
    font-size: 0.9rem;
}

.box-model-explanation ul {
    text-align: left;
    max-width: 400px;
    margin: var(--spacing-large) auto;
    list-style-position: inside;
}

.box-model-explanation li {
    margin-bottom: var(--spacing-medium);
}

/* ============================================
   EJEMPLOS PRÁCTICOS
   ============================================ */

.example {
    margin-bottom: var(--spacing-large);
    padding-bottom: var(--spacing-medium);
    border-bottom: 1px solid var(--color-light);
}

.example:last-child {
    border-bottom: none;
}

.example h3 {
    color: var(--color-primary);
    margin-top: 0;
}

.example-preview {
    background: linear-gradient(135deg, var(--color-bg-light) 0%, var(--color-bg-lighter) 100%);
    padding: var(--spacing-xl);
    border-radius: var(--radius-large);
    border: 2px dashed var(--color-primary);
    margin: var(--spacing-large) 0;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 120px;
}

/* Botón elegante */
.btn-elegant {
    background-color: var(--color-primary);
    color: var(--color-white);
    padding: 10px 18px;
    border: none;
    border-radius: var(--radius-medium);
    cursor: pointer;
    font-weight: bold;
    font-size: 0.9rem;
    transition: all 0.3s ease;
    box-shadow: var(--shadow-medium);
}

.btn-elegant:hover {
    background-color: var(--color-primary-dark);
    transform: translateY(-2px);
    box-shadow: var(--shadow-large);
}

.btn-elegant:active {
    transform: translateY(0);
}

/* Tarjeta de ejemplo */
.card-example {
    background-color: var(--color-bg-lighter);
    border-radius: var(--radius-large);
    padding: var(--spacing-large);
    box-shadow: var(--shadow-medium);
    max-width: 300px;
    text-align: center;
}

.card-example h4 {
    color: var(--color-primary);
    margin-bottom: var(--spacing-small);
    font-size: 1rem;
}

.card-example p {
    font-size: 0.95rem;
    color: var(--color-text-secondary);
    margin-bottom: 0;
}

/* Grid responsivo */
.grid-example {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
    gap: var(--spacing-medium);
    width: 100%;
}

.grid-item {
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
    color: var(--color-white);
    padding: var(--spacing-large);
    border-radius: var(--radius-large);
    text-align: center;
    font-weight: bold;
    box-shadow: var(--shadow-medium);
    transition: all 0.3s ease;
}

.grid-item:hover {
    transform: scale(1.05);
    box-shadow: var(--shadow-large);
}

/* ============================================
   CONSEJOS FINALES
   ============================================ */

.final-tips {
    background: linear-gradient(135deg, rgba(0, 168, 255, 0.08) 0%, rgba(0, 168, 255, 0.15) 100%);
}

.tips-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-large);
    margin-top: var(--spacing-medium);
}

.tip {
    background-color: var(--color-bg-light);
    padding: var(--spacing-large);
    border-radius: var(--radius-large);
    box-shadow: var(--shadow-small);
    transition: all 0.3s ease;
    border-left: 4px solid var(--color-primary);
}

.tip:hover {
    box-shadow: var(--shadow-medium);
    transform: translateY(-4px);
}

.tip h3 {
    color: var(--color-primary);
    margin-top: 0;
    font-size: 1.1rem;
}

.tip p {
    margin-bottom: 0;
    color: var(--color-text-secondary);
}

/* ============================================
   UNIDADES DE MEDIDA
   ============================================ */

.units-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-large);
    margin: var(--spacing-large) 0;
}

.unit-card {
    background-color: var(--color-bg-light);
    padding: var(--spacing-large);
    border-radius: var(--radius-large);
    border-left: 4px solid var(--color-primary);
    transition: all 0.3s ease;
}

.unit-card:hover {
    box-shadow: var(--shadow-medium);
    transform: translateY(-4px);
}

.unit-card h3 {
    color: var(--color-primary);
    margin-top: 0;
    font-size: 1rem;
}

.unit-card p {
    font-size: 0.9rem;
    margin-bottom: var(--spacing-small);
}

/* Info Box */
.info-box {
    background: linear-gradient(135deg, rgba(0, 168, 255, 0.15) 0%, rgba(0, 168, 255, 0.08) 100%);
    border-left: 4px solid var(--color-primary);
    padding: var(--spacing-large);
    border-radius: var(--radius-medium);
    margin: var(--spacing-large) 0;
}

.info-box h3 {
    color: var(--color-primary);
    margin-top: 0;
}

.info-box ul {
    margin: var(--spacing-medium) 0 0 var(--spacing-xl);
    list-style-position: inside;
}

.info-box li {
    margin-bottom: var(--spacing-small);
}

/* Cascada Info */
.cascade-info {
    background-color: var(--color-bg-light);
    padding: var(--spacing-large);
    border-radius: var(--radius-medium);
    margin: var(--spacing-medium) 0;
    border-left: 4px solid var(--color-primary);
}

.cascade-info h4 {
    color: var(--color-primary);
    margin-top: 0;
    margin-bottom: var(--spacing-small);
}

.cascade-info ol,
.cascade-info p {
    margin-bottom: var(--spacing-medium);
}

/* Explanation Box */
.explanation-box {
    background-color: var(--color-bg-light);
    padding: var(--spacing-large);
    border-radius: var(--radius-medium);
    border-left: 4px solid var(--color-success);
    margin: var(--spacing-large) 0;
    font-style: italic;
}

/* ============================================
   SELECTORES Y ESPECIFICIDAD
   ============================================ */

.specificity-table {
    background-color: var(--color-bg-light);
    border-radius: var(--radius-medium);
    overflow: hidden;
    margin: var(--spacing-large) 0;
}

.specificity-row {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr;
    padding: var(--spacing-medium);
    border-bottom: 1px solid var(--color-light);
    font-size: 0.9rem;
}

.specificity-row:last-child {
    border-bottom: none;
}

.specificity-row:nth-child(odd) {
    background-color: var(--color-bg-darker);
}

.specificity-selector {
    font-weight: bold;
    color: var(--color-primary);
}

.specificity-level {
    color: var(--color-primary);
}

.specificity-use {
    color: var(--color-text-secondary);
}

/* ============================================
   POSICIONAMIENTO
   ============================================ */

.position-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-large);
    margin: var(--spacing-large) 0;
}

.position-card {
    background-color: var(--color-bg-light);
    padding: var(--spacing-large);
    border-radius: var(--radius-large);
    border: 2px solid transparent;
    transition: all 0.3s ease;
    border-left-width: 4px;
    border-left-color: var(--color-primary);
}

.position-card:hover {
    box-shadow: var(--shadow-medium);
    transform: translateY(-4px);
}

.position-card h3 {
    color: var(--color-primary);
    margin-top: 0;
    font-size: 1rem;
}

.position-card p {
    margin-bottom: 0;
    font-size: 0.9rem;
}

/* ============================================
   FLEXBOX
   ============================================ */

.flexbox-explanation {
    margin: var(--spacing-large) 0;
}

.concept-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-large);
    margin: var(--spacing-large) 0;
}

.concept-item {
    background-color: var(--color-bg-light);
    padding: var(--spacing-large);
    border-radius: var(--radius-large);
    border-left: 4px solid var(--color-primary);
}

.concept-item h4 {
    color: var(--color-primary);
    margin-top: 0;
}

.concept-item p {
    margin-bottom: 0;
    font-size: 0.9rem;
}

.flexbox-example {
    background-color: var(--color-bg-light);
    padding: var(--spacing-large);
    border-radius: var(--radius-large);
    margin: var(--spacing-large) 0;
    border-left: 4px solid var(--color-success);
}

/* ============================================
   PSEUDO-CLASES Y PSEUDO-ELEMENTOS
   ============================================ */

.pseudo-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-large);
    margin: var(--spacing-large) 0;
}

.pseudo-card {
    background-color: var(--color-bg-light);
    padding: var(--spacing-large);
    border-radius: var(--radius-large);
    border: 2px solid transparent;
    transition: all 0.3s ease;
    border-left-width: 4px;
    border-left-color: var(--color-primary);
}

.pseudo-card:hover {
    box-shadow: var(--shadow-medium);
    transform: translateY(-4px);
}

.pseudo-card h3 {
    color: var(--color-primary);
    margin-top: 0;
    font-size: 1rem;
}

/* ============================================
   RESPONSIVE DESIGN
   ============================================ */

.responsive-explanation {
    background-color: var(--color-bg-light);
    padding: var(--spacing-large);
    border-radius: var(--radius-large);
    margin: var(--spacing-large) 0;
}

.responsive-explanation h3 {
    color: var(--color-primary);
}

.breakpoints-table {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-large);
    margin: var(--spacing-large) 0;
}

.breakpoint-item {
    background-color: var(--color-bg-darker);
    padding: var(--spacing-large);
    border-radius: var(--radius-large);
    text-align: center;
    border: 2px solid var(--color-bg-light);
}

.breakpoint-item h4 {
    color: var(--color-primary);
    margin-top: 0;
}

.breakpoint-item p {
    margin: var(--spacing-small) 0;
    font-size: 0.9rem;
}

/* ============================================
   ANIMACIONES
   ============================================ */

.animation-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-large);
    margin: var(--spacing-large) 0;
}

.animation-card {
    background-color: var(--color-bg-light);
    padding: var(--spacing-large);
    border-radius: var(--radius-large);
    border-left: 4px solid var(--color-primary);
}

.animation-card h3 {
    color: var(--color-primary);
    margin-top: 0;
}

.animation-card p {
    margin-bottom: var(--spacing-small);
    font-size: 0.9rem;
}

/* ============================================
   RECURSOS Y PRÓXIMOS PASOS
   ============================================ */

.resources-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-large);
    margin: var(--spacing-large) 0;
}

.resource {
    background-color: var(--color-bg-light);
    padding: var(--spacing-large);
    border-radius: var(--radius-large);
    border: 2px solid transparent;
    transition: all 0.3s ease;
}

.resource:hover {
    border-color: var(--color-primary);
    box-shadow: var(--shadow-medium);
}

.resource h3 {
    color: var(--color-primary);
    margin-top: 0;
}

.resource ul {
    list-style-position: inside;
    margin: 0;
    padding: 0;
}

.resource li {
    margin-bottom: var(--spacing-small);
    font-size: 0.9rem;
}

/* Final Message */
.final-message {
    background: linear-gradient(135deg, rgba(40, 167, 69, 0.15) 0%, rgba(40, 167, 69, 0.08) 100%);
    border-left: 4px solid var(--color-success);
    padding: var(--spacing-large);
    border-radius: var(--radius-large);
    margin: var(--spacing-large) 0;
}

.final-message h3 {
    color: var(--color-success);
    margin-top: 0;
}

.tips-list {
    list-style-position: inside;
    margin: var(--spacing-medium) 0 0 0;
    padding: 0;
}

.tips-list li {
    margin-bottom: var(--spacing-medium);
    line-height: 1.8;
    font-size: 0.95rem;
}

/* ============================================
   BOX MODEL DETAILS
   ============================================ */

.box-model-details {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-large);
    margin: var(--spacing-large) 0;
}

.detail-item {
    background-color: var(--color-bg-darker);
    padding: var(--spacing-large);
    border-radius: var(--radius-medium);
    border-left: 4px solid var(--color-primary);
}

.detail-item h4 {
    color: var(--color-primary);
    margin-top: 0;
}

.detail-item p {
    margin-bottom: 0;
    font-size: 0.9rem;
}

.example-box {
    background-color: var(--color-bg-dark);
    padding: var(--spacing-large);
    border-radius: var(--radius-medium);
    margin: var(--spacing-large) 0;
}

.example-box h4 {
    color: var(--color-primary);
    margin-top: 0;
}

/* ============================================
   METHOD INFO
   ============================================ */

.method-info {
    background-color: var(--color-bg-darker);
    padding: var(--spacing-medium);
    border-radius: var(--radius-small);
    margin-top: var(--spacing-small);
    font-size: 0.9rem;
    color: var(--color-text-secondary);
}

/* ============================================
   STRUCTURE EXPLANATION
   ============================================ */

.structure-explanation {
    font-size: 0.8rem;
    color: var(--color-text-secondary);
    display: block;
    margin-top: 4px;
}

/* ============================================
   SIDEBAR - TABLA DE CONTENIDOS
   ============================================ */

.sidebar {
    width: 100%;
    margin-bottom: var(--spacing-xl);
    margin-left: auto;
    margin-right: auto;
}

.toc-box {
    background: linear-gradient(135deg, var(--color-bg-light) 0%, #252525 100%);
    padding: var(--spacing-xl) var(--spacing-2xl);
    border-radius: var(--radius-large);
    box-shadow: 
        0 10px 30px rgba(0, 0, 0, 0.5),
        0 0 20px rgba(0, 168, 255, 0.1);
    border-bottom: 3px solid var(--color-primary);
    position: relative;
    overflow-x: auto;
    overflow-y: hidden;
}

.toc-box::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 2px;
    background: linear-gradient(180deg, var(--color-primary), transparent);
}

.toc-box h3 {
    color: var(--color-primary);
    font-size: 1.3rem;
    margin-top: 0;
    margin-bottom: var(--spacing-large);
    font-weight: 700;
    letter-spacing: 0.5px;
    display: flex;
    align-items: center;
    gap: var(--spacing-medium);
}

.toc-list {
    list-style: none;
    margin: 0;
    padding: 0;
    counter-reset: toc-counter;
    display: flex;
    flex-direction: row;
    gap: var(--spacing-medium);
    flex-wrap: wrap;
    align-items: center;
}

.toc-list li {
    margin-bottom: 0;
    counter-increment: toc-counter;
    white-space: nowrap;
}

.toc-list li::before {
    content: counter(toc-counter);
    display: inline-block;
    width: 24px;
    height: 24px;
    background: linear-gradient(135deg, var(--color-primary), #0088cc);
    color: white;
    text-align: center;
    line-height: 24px;
    border-radius: 50%;
    font-size: 0.75rem;
    font-weight: 700;
    margin-right: var(--spacing-small);
    flex-shrink: 0;
}

.toc-list a {
    color: var(--color-text-primary);
    text-decoration: none;
    display: inline-flex;
    align-items: center;
    padding: var(--spacing-small) var(--spacing-medium);
    border-radius: var(--radius-medium);
    transition: all 0.4s cubic-bezier(0.25, 0.46, 0.45, 0.94);
    font-size: 0.9rem;
    line-height: 1.5;
    position: relative;
    background-color: transparent;
    border: 1px solid transparent;
}

.toc-list a::before {
    content: '';
    position: absolute;
    left: 0;
    bottom: -3px;
    right: 0;
    height: 3px;
    background-color: var(--color-primary);
    border-radius: 3px 3px 0 0;
    transform: scaleX(0);
    transform-origin: left;
    transition: transform 0.4s cubic-bezier(0.25, 0.46, 0.45, 0.94);
}

.toc-list a:hover {
    background: rgba(0, 168, 255, 0.15);
    color: var(--color-primary);
    border: 1px solid var(--color-primary);
    transform: translateY(-2px);
}

.toc-list a:hover::before {
    transform: scaleY(1);
}

/* ============================================
   FOOTER
   ============================================ */

.footer {
    background-color: var(--color-bg-darker);
    color: var(--color-text-primary);
    text-align: center;
    padding: var(--spacing-xl);
    margin-top: var(--spacing-2xl);
    border-top: 2px solid var(--color-bg-lighter);
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
}

.footer p {
    margin-bottom: var(--spacing-small);
    font-size: 0.9rem;
}

.footer p:last-child {
    margin-bottom: 0;
}

/* ============================================
   RESPONSIVENESS
   ============================================ */

@media (max-width: 768px) {
    .header h1 {
        font-size: 1.8rem;
    }

    .subtitle {
        font-size: 1rem;
    }

    .nav-list {
        flex-direction: column;
    }

    .nav-list li {
        max-width: 100%;
    }

    .container {
        padding: var(--spacing-large);
    }

    .section {
        padding: var(--spacing-xl);
    }

    .section h2 {
        font-size: 1.5rem;
    }

    .section h3 {
        font-size: 1.2rem;
    }

    .selector-grid {
        grid-template-columns: 1fr;
    }

    .properties-grid {
        grid-template-columns: 1fr;
    }

    .tips-container {
        grid-template-columns: 1fr;
    }

    .structure {
        font-size: 0.9rem;
    }

    .property-card,
    .selector-card {
        padding: var(--spacing-xl);
    }
}

@media (max-width: 480px) {
    .header h1 {
        font-size: 1.3rem;
    }

    .section {
        padding: var(--spacing-large);
        margin-bottom: var(--spacing-large);
    }

    .code-block {
        font-size: 0.8rem;
        padding: var(--spacing-xl);
    }

    .property-card h3,
    .selector-card h3 {
        font-size: 1rem;
    }

    .method {
        padding: var(--spacing-medium);
    }
}

/* ============================================
   ANIMACIONES Y TRANSICIONES
   ============================================ */

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

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

/* ============================================
   IMPRESIÓN
   ============================================ */

@media print {
    .navbar,
    .footer {
        display: none;
    }

    .section {
        page-break-inside: avoid;
        box-shadow: none;
        border: 1px solid #ccc;
    }
}