/* ===== Variables y reset ===== */
:root {
  --color-primary: #4F46E5;
  --color-primary-light: #818CF8;
  --color-primary-lighter: #C7D2FE;
  --color-accent: #00C9A7;
  --color-warn: #FF6B6B;
  --color-bg: #F7F7FB;
  --color-surface: #FFFFFF;
  --color-text: #1E1B2E;
  --color-text-soft: #5B5570;
  --color-border: #E7E5F5;
  --radius-lg: 20px;
  --radius-md: 14px;
  --radius-sm: 8px;
  --shadow-sm: 0 2px 8px rgba(79, 70, 229, 0.08);
  --shadow-md: 0 8px 24px rgba(79, 70, 229, 0.12);
  --sidebar-w: 270px;
  --font: 'Poppins', 'Segoe UI', Arial, sans-serif;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: var(--font);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  overflow-x: hidden;
}

img { max-width: 100%; display: block; }

a { color: inherit; text-decoration: none; }

ul { list-style: none; }

button, input, select { font-family: inherit; }

::selection { background: var(--color-primary-lighter); }

/* ===== Layout general ===== */
.layout {
  display: flex;
  min-height: 100vh;
}

/* ===== Sidebar ===== */
.sidebar {
  width: var(--sidebar-w);
  flex-shrink: 0;
  background: var(--color-surface);
  border-right: 1px solid var(--color-border);
  position: fixed;
  top: 0;
  left: 0;
  bottom: 0;
  overflow-y: auto;
  z-index: 100;
  transition: transform 0.3s ease;
}

.sidebar__brand {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 22px 20px;
  border-bottom: 1px solid var(--color-border);
}

.sidebar__brand img { width: 38px; height: 38px; }

.sidebar__brand h1 {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--color-primary);
}

.sidebar__brand span {
  display: block;
  font-size: 0.72rem;
  color: var(--color-text-soft);
  font-weight: 400;
}

.nav__list { padding: 14px 10px 30px; }

.nav__link {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 12px;
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--color-text-soft);
  margin-bottom: 4px;
  transition: background 0.2s ease, color 0.2s ease, transform 0.2s ease;
}

.nav__link .nav__icon {
  width: 20px;
  height: 20px;
  flex-shrink: 0;
  opacity: 0.85;
}

.nav__link:hover {
  background: var(--color-bg);
  color: var(--color-primary);
  transform: translateX(2px);
}

.nav__link.active {
  background: linear-gradient(135deg, var(--color-primary), #6D5BF7);
  color: #fff;
  box-shadow: var(--shadow-sm);
}

.nav__link.active .nav__icon { opacity: 1; }

/* ===== Contenido principal ===== */
.main {
  margin-left: var(--sidebar-w);
  flex: 1;
  min-width: 0;
  padding: 0 0 60px;
}

/* ===== Topbar móvil ===== */
.topbar {
  display: none;
  align-items: center;
  justify-content: space-between;
  padding: 14px 18px;
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 90;
}

.topbar__brand { display: flex; align-items: center; gap: 8px; font-weight: 700; color: var(--color-primary); }
.topbar__brand img { width: 30px; height: 30px; }

.hamburger {
  width: 40px;
  height: 40px;
  border: none;
  background: var(--color-bg);
  border-radius: var(--radius-sm);
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 4px;
}

.hamburger span {
  width: 20px;
  height: 2px;
  background: var(--color-primary);
  border-radius: 2px;
}

/* ===== Hero ===== */
.hero {
  background: linear-gradient(135deg, #4F46E5 0%, #6D5BF7 45%, #00C9A7 100%);
  color: #fff;
  padding: 70px 50px;
  border-radius: 0 0 40px 40px;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: "";
  position: absolute;
  width: 400px;
  height: 400px;
  background: rgba(255,255,255,0.08);
  border-radius: 50%;
  top: -150px;
  right: -100px;
}

.hero__content { max-width: 620px; position: relative; z-index: 1; }

.hero__eyebrow {
  display: inline-block;
  background: rgba(255,255,255,0.18);
  padding: 6px 14px;
  border-radius: 30px;
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.5px;
  margin-bottom: 18px;
}

.hero h2 {
  font-size: clamp(1.8rem, 4vw, 2.7rem);
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: 16px;
}

.hero p {
  font-size: 1.02rem;
  opacity: 0.92;
  margin-bottom: 26px;
  max-width: 520px;
}

.hero__actions { display: flex; gap: 14px; flex-wrap: wrap; }

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 24px;
  border-radius: 30px;
  font-weight: 600;
  font-size: 0.92rem;
  cursor: pointer;
  border: none;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.btn:hover { transform: translateY(-2px); }

.btn--light { background: #fff; color: var(--color-primary); }
.btn--light:hover { box-shadow: 0 6px 20px rgba(0,0,0,0.18); }

.btn--outline { background: transparent; color: #fff; border: 1.5px solid rgba(255,255,255,0.6); }
.btn--outline:hover { background: rgba(255,255,255,0.12); }

.btn--primary { background: var(--color-primary); color: #fff; }
.btn--primary:hover { box-shadow: var(--shadow-md); }

.btn--accent { background: var(--color-accent); color: #fff; }
.btn--accent:hover { box-shadow: 0 6px 18px rgba(0,201,167,0.35); }

.btn--sm { padding: 8px 16px; font-size: 0.82rem; }

/* ===== Secciones ===== */
.section {
  padding: 70px 50px 20px;
  scroll-margin-top: 20px;
  max-width: 1180px;
}

.section__header { margin-bottom: 30px; }

.section__tag {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 10px;
}

.section__tag img { width: 40px; height: 40px; }

.section__tag span {
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 1px;
  text-transform: uppercase;
  color: var(--color-accent);
}

.section__header h2 {
  font-size: clamp(1.5rem, 3vw, 2rem);
  font-weight: 700;
  color: var(--color-text);
}

.section__header p.lead {
  color: var(--color-text-soft);
  font-size: 1rem;
  max-width: 720px;
  margin-top: 8px;
}

/* Reveal animation */
.reveal {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.reveal.is-visible { opacity: 1; transform: translateY(0); }

/* ===== Cards ===== */
.grid {
  display: grid;
  gap: 20px;
  grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
  margin-bottom: 26px;
}

.card {
  background: var(--color-surface);
  border-radius: var(--radius-md);
  padding: 22px;
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--color-border);
  transition: transform 0.25s ease, box-shadow 0.25s ease;
}

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

.card h3 {
  font-size: 1.02rem;
  margin-bottom: 8px;
  color: var(--color-primary);
}

.card p { font-size: 0.9rem; color: var(--color-text-soft); }

.card .formula {
  background: var(--color-bg);
  border-radius: var(--radius-sm);
  padding: 12px 14px;
  font-family: 'Cambria Math', Georgia, serif;
  font-size: 1.05rem;
  margin: 10px 0;
  color: var(--color-primary);
  text-align: center;
}

/* ===== Panel interactivo (calculadoras) ===== */
.panel {
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-sm);
  padding: 28px;
  margin-bottom: 30px;
}

.panel__title {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  font-size: 1rem;
  margin-bottom: 18px;
  color: var(--color-text);
}

.panel__title .dot {
  width: 10px; height: 10px; border-radius: 50%; background: var(--color-accent);
}

.field-row { display: flex; gap: 14px; flex-wrap: wrap; align-items: flex-end; margin-bottom: 16px; }

.field { display: flex; flex-direction: column; gap: 6px; flex: 1; min-width: 180px; }

.field label { font-size: 0.82rem; font-weight: 600; color: var(--color-text-soft); }

.field input[type="text"],
.field input[type="number"],
.field select,
.field textarea {
  padding: 11px 14px;
  border-radius: var(--radius-sm);
  border: 1.5px solid var(--color-border);
  font-size: 0.92rem;
  background: var(--color-bg);
  color: var(--color-text);
  transition: border-color 0.2s ease;
}

.field textarea { resize: vertical; min-height: 70px; font-family: monospace; }

.field input:focus, .field select:focus, .field textarea:focus {
  outline: none;
  border-color: var(--color-primary);
  background: #fff;
}

.field--check { flex-direction: row; align-items: center; gap: 8px; }

.result-box {
  background: linear-gradient(135deg, #EEF0FF, #E6FBF7);
  border-radius: var(--radius-md);
  padding: 18px 20px;
  margin-top: 8px;
}

.result-box.hidden { display: none; }

.result-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 14px;
}

.result-item .label {
  font-size: 0.75rem;
  color: var(--color-text-soft);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  font-weight: 600;
}

.result-item .value {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--color-primary);
}

.hint {
  font-size: 0.8rem;
  color: var(--color-text-soft);
  margin-top: 6px;
}

.error-msg {
  color: var(--color-warn);
  font-size: 0.85rem;
  font-weight: 600;
  margin-top: 8px;
}

/* ===== Canvas de gráficos ===== */
.chart-wrap {
  background: var(--color-bg);
  border-radius: var(--radius-md);
  padding: 16px;
  display: flex;
  justify-content: center;
  overflow-x: auto;
}

canvas { max-width: 100%; }

/* ===== Tabla de frecuencias ===== */
.freq-table-wrap { overflow-x: auto; margin-top: 14px; }

table.freq-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.88rem;
  min-width: 480px;
}

table.freq-table th, table.freq-table td {
  padding: 10px 12px;
  text-align: center;
  border-bottom: 1px solid var(--color-border);
}

table.freq-table th {
  background: var(--color-primary);
  color: #fff;
  font-weight: 600;
  font-size: 0.78rem;
  text-transform: uppercase;
}

table.freq-table tr:nth-child(even) { background: var(--color-bg); }

/* ===== Tabs (tipo de gráfico / distribución) ===== */
.tabs { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 18px; }

.tab-btn {
  padding: 9px 18px;
  border-radius: 30px;
  border: 1.5px solid var(--color-border);
  background: var(--color-surface);
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--color-text-soft);
  cursor: pointer;
  transition: all 0.2s ease;
}

.tab-btn:hover { border-color: var(--color-primary-light); color: var(--color-primary); }

.tab-btn.active {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: #fff;
}

/* ===== Quiz clasificador (tipos de variable) ===== */
.quiz-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  background: var(--color-bg);
  border-radius: var(--radius-sm);
  padding: 12px 16px;
  margin-bottom: 10px;
  flex-wrap: wrap;
}

.quiz-item .quiz-text { font-weight: 500; font-size: 0.92rem; }

.quiz-item .quiz-btns { display: flex; gap: 8px; }

.quiz-item button {
  padding: 7px 14px;
  border-radius: 20px;
  border: 1.5px solid var(--color-border);
  background: #fff;
  font-size: 0.78rem;
  font-weight: 600;
  cursor: pointer;
}

.quiz-item button.correct { background: var(--color-accent); color: #fff; border-color: var(--color-accent); }
.quiz-item button.wrong { background: var(--color-warn); color: #fff; border-color: var(--color-warn); }

/* ===== Definición destacada ===== */
.definition {
  border-left: 4px solid var(--color-accent);
  background: #F0FBF9;
  padding: 16px 20px;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  margin-bottom: 20px;
  font-size: 0.95rem;
}

.definition strong { color: var(--color-primary); }

/* ===== Footer ===== */
.footer {
  margin-top: 40px;
  padding: 30px 50px;
  text-align: center;
  color: var(--color-text-soft);
  font-size: 0.85rem;
  border-top: 1px solid var(--color-border);
}

/* ===== Overlay móvil ===== */
.overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(30,27,46,0.5);
  z-index: 95;
}

.overlay.show { display: block; }

/* ===== Responsive ===== */
@media (max-width: 960px) {
  .sidebar { transform: translateX(-100%); }
  .sidebar.open { transform: translateX(0); box-shadow: var(--shadow-md); }
  .main { margin-left: 0; }
  .topbar { display: flex; }
  .hero, .section { padding-left: 24px; padding-right: 24px; }
  .hero { border-radius: 0 0 24px 24px; padding-top: 44px; padding-bottom: 44px; }
}

@media (max-width: 560px) {
  .field-row { flex-direction: column; align-items: stretch; }
  .section { padding-top: 46px; }
}