/* assets/css/style.css */
:root {
    --primary: #3182ce;
    --primary-dark: #2b6cb0;
    --bg: #f7fafc;
    --panel: #ffffff;
    --text: #2d3748;
    --muted: #718096;
    --border: #e2e8f0;
    --shadow: 0 4px 6px rgba(0,0,0,0.05);
    
    /* Variables para el cintillo oscuro */
    --header-bg: #1a202c; 
    --header-text: #cbd5e0;
}

* { box-sizing: border-box; }

body { 
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; 
    line-height: 1.6; 
    margin: 0; 
    color: var(--text); 
    background-color: var(--bg); 
}

a { text-decoration: none; color: var(--primary); }
img { max-width: 100%; height: auto; }

/* Contenedor Base */
.container { max-width: 1100px; margin: 0 auto; padding: 0 20px; }

/* Cintillo Superior Oscuro y Fijo */
.site-header { 
    background: var(--header-bg); 
    padding: 1rem 5%; 
    display: flex; 
    justify-content: space-between; 
    align-items: center; 
    box-shadow: 0 2px 10px rgba(0,0,0,0.15);
    
    /* Estas tres líneas anclan el menú a la parte superior */
    position: sticky;
    top: 0;
    z-index: 1000;
}
.site-header a.logo { 
    color: var(--primary); 
    font-size: 1.5rem; 
    font-weight: bold; 
    letter-spacing: 1px; 
}
.site-nav { display: flex; align-items: center; }
.site-nav a { 
    color: var(--header-text); 
    margin-left: 20px; 
    font-weight: 500; 
    transition: color 0.3s ease; 
    font-size: 0.95rem;
}
.site-nav a:hover { color: #fff; }

/* Secciones y Tarjetas */
section { padding: 40px 0; }
.card { 
    background: var(--panel); 
    padding: 25px; 
    border-radius: 12px; 
    border: 1px solid var(--border); 
    box-shadow: var(--shadow);
    transition: transform 0.2s;
}
.card:hover { transform: translateY(-5px); }

/* Botones */
.btn { 
    padding: 10px 20px; 
    border-radius: 6px; 
    font-weight: bold; 
    display: inline-block; 
    cursor: pointer; 
    transition: background 0.3s;
}
.btn-primary { background: var(--primary); color: #fff; border: none; }
.btn-primary:hover { background: var(--primary-dark); }
.btn-secondary { background: transparent; border: 1px solid var(--header-text); color: var(--header-text); }
.btn-secondary:hover { border-color: #fff; color: #fff; }

/* Ajuste para fórmulas LaTeX */
.MathJax { font-size: 1.1rem; }

/* =========================================
   BOTÓN FLOTANTE MULTI-REDES (FAB)
   ========================================= */
.fab-container {
  position: fixed;
  bottom: 25px;
  right: 25px;
  z-index: 9998;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

.fab-menu {
  display: flex;
  flex-direction: column;
  gap: 10px;
  opacity: 0;
  visibility: hidden;
  transform: translateY(20px);
  transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
}

.fab-container.active .fab-menu {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.fab-item {
  width: 45px;
  height: 45px;
  border-radius: 50%;
  background-color: var(--panel);
  border: 1px solid var(--border);
  display: flex;
  justify-content: center;
  align-items: center;
  transition: 0.3s ease;
  box-shadow: var(--shadow);
}

.fab-item svg {
  width: 22px;
  height: 22px;
  fill: var(--muted);
  transition: 0.3s;
}

/* Colores de marca en hover */
.fab-item.wa:hover { background-color: #25D366; border-color: #25D366; }
.fab-item.fb:hover { background-color: #1877F2; border-color: #1877F2; }
.fab-item.ig:hover { background-color: #E4405F; border-color: #E4405F; }
.fab-item.tk:hover { background-color: #000000; border-color: #000000; }
.fab-item.yt:hover { background-color: #FF0000; border-color: #FF0000; }
.fab-item.tg:hover { background-color: #0088cc; border-color: #0088cc; }
.fab-item:hover svg { fill: #ffffff; }

/* Botón Principal Azul */
.fab-main {
  width: 60px;
  height: 60px;
  border-radius: 50%;
  background: var(--primary);
  color: #fff;
  border: none;
  cursor: pointer;
  display: flex;
  justify-content: center;
  align-items: center;
  box-shadow: 0 10px 25px rgba(49, 130, 206, 0.35);
  transition: 0.3s ease;
}

.fab-main:hover {
  transform: scale(1.05);
  background: var(--primary-dark);
}

.fab-main svg {
  width: 28px;
  height: 28px;
  fill: currentColor;
  transition: transform 0.3s ease;
}

.fab-container.active .fab-main svg {
  transform: rotate(45deg);
}

/* Estilos para imágenes dentro de lecciones y artículos */
.img-contenido {
    max-width: 100%;
    height: auto;
    display: block;
    margin: 30px auto;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
}