/* ============================================================
   Base: reset + tipografía + layout primitives
   ============================================================ */

*, *::before, *::after { box-sizing: border-box; }

html {
  -webkit-text-size-adjust: 100%;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
  scroll-behavior: smooth;
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: var(--font-sans);
  font-size: var(--fs-base);
  line-height: var(--lh-normal);
  font-feature-settings: "ss01", "ss02", "cv11";
  min-height: 100vh;
  overflow-x: hidden;
}

/* Fondo de retícula milimétrica muy sutil (toque científico) */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  background-image:
    linear-gradient(var(--paper-grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--paper-grid) 1px, transparent 1px);
  background-size: 80px 80px;
  mask-image: radial-gradient(ellipse at center, #000 30%, transparent 75%);
  -webkit-mask-image: radial-gradient(ellipse at center, #000 30%, transparent 75%);
}

main, header, footer, section { position: relative; z-index: 1; }

h1, h2, h3, h4, h5, h6 {
  margin: 0;
  font-weight: 500;
  letter-spacing: -0.02em;
  line-height: var(--lh-tight);
  color: var(--fg);
}
h1 { font-size: var(--fs-3xl); letter-spacing: -0.035em; font-weight: 500; }
h2 { font-size: var(--fs-2xl); letter-spacing: -0.03em; }
h3 { font-size: var(--fs-xl); }
h4 { font-size: var(--fs-lg); }

p { margin: 0 0 1em; color: var(--fg-muted); line-height: var(--lh-normal); text-wrap: pretty; }
p:last-child { margin-bottom: 0; }

a { color: inherit; text-decoration: none; }
a:focus-visible, button:focus-visible, input:focus-visible, textarea:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

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

hr { border: 0; height: 1px; background: var(--border); margin: 0; }

code, .mono { font-family: var(--font-mono); font-size: 0.92em; }

/* ---------- Container ---------- */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

/* ---------- Eyebrow / label ---------- */
.eyebrow {
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--fg-faint);
  display: inline-flex;
  align-items: center;
  gap: 10px;
}
.eyebrow::before {
  content: "";
  width: 22px;
  height: 1px;
  background: currentColor;
  opacity: 0.5;
}

/* Figura numerada tipo paper académico */
.fig-tag {
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--fg-faint);
}

/* ---------- Buttons ---------- */
.btn {
  --btn-bg: var(--fg);
  --btn-fg: var(--bg);
  --btn-bd: var(--fg);
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 14px 22px;
  font-family: var(--font-sans);
  font-size: var(--fs-sm);
  font-weight: 500;
  letter-spacing: 0.01em;
  background: var(--btn-bg);
  color: var(--btn-fg);
  border: 1px solid var(--btn-bd);
  border-radius: 999px;
  cursor: pointer;
  transition: background var(--t) var(--ease), color var(--t) var(--ease), transform var(--t) var(--ease);
  text-align: center;
  line-height: 1;
}
.btn:hover { transform: translateY(-1px); }

.btn--primary {
  --btn-bg: var(--accent);
  --btn-fg: #0B2A3B;
  --btn-bd: var(--accent);
}
:root[data-theme="dark"] .btn--primary { --btn-fg: #0A1519; }

.btn--ghost {
  --btn-bg: transparent;
  --btn-fg: var(--fg);
  --btn-bd: var(--border-strong);
}
.btn--ghost:hover { --btn-bg: var(--bg-elev); }

.btn--link {
  background: transparent;
  color: var(--fg);
  border: 0;
  padding: 0;
  border-radius: 0;
  border-bottom: 1px solid currentColor;
  padding-bottom: 3px;
  gap: 6px;
}
.btn--link:hover { color: var(--accent); }

.btn .arrow {
  transition: transform var(--t) var(--ease);
}
.btn:hover .arrow { transform: translateX(3px); }

/* ---------- Section spacing ---------- */
.section {
  padding-block: clamp(72px, 10vw, 144px);
  position: relative;
}
.section--tight { padding-block: clamp(48px, 6vw, 88px); }

.section-head {
  display: grid;
  grid-template-columns: 1fr;
  gap: 16px;
  margin-bottom: clamp(40px, 5vw, 72px);
  max-width: 900px;
}
.section-head h2 { margin-top: 4px; }

/* ---------- Rules (líneas finas entre secciones) ---------- */
.rule-top { border-top: 1px solid var(--border); }
.rule-bottom { border-bottom: 1px solid var(--border); }

/* ---------- Reveal on scroll ---------- */
[data-reveal] {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity 700ms var(--ease-out), transform 700ms var(--ease-out);
  transition-delay: var(--delay, 0ms);
}
[data-reveal].is-visible { opacity: 1; transform: none; }

/* ---------- Screen reader only ---------- */
.sr-only {
  position: absolute; width: 1px; height: 1px;
  padding: 0; margin: -1px; overflow: hidden;
  clip: rect(0,0,0,0); white-space: nowrap; border: 0;
}

/* ---------- Skip link ---------- */
.skip-link {
  position: absolute; top: -40px; left: 12px;
  background: var(--fg); color: var(--bg);
  padding: 8px 14px; font-size: var(--fs-sm);
  z-index: 100; border-radius: var(--radius);
}
.skip-link:focus { top: 12px; }

::selection { background: var(--accent); color: #0B2A3B; }