:root {
    --bg: #0f172a;       /* slate-900 */
    --card: #111827;     /* gray-900 */
    --muted: #94a3b8;    /* slate-400 */
    --text: #e5e7eb;     /* gray-200 */
    --accent: #af0000;   /* cyan-400 */
    --accent-2: #f83838; /* sky-400 */
  }
  
  html, body { height: 100%; }
  body {
    margin: 0;
    font-family: system-ui, -apple-system, Segoe UI, Roboto, Ubuntu, Cantarell, Noto Sans, "Helvetica Neue", Arial, "Apple Color Emoji", "Segoe UI Emoji";
    background: linear-gradient(180deg, #0b1220 0%, var(--bg) 40%, #0b1220 100%);
    color: var(--text);
    line-height: 1.6;
  }
  
  header {
    position: sticky;
    top: 0;
    z-index: 10;
    backdrop-filter: blur(6px);
    background: rgba(15, 23, 42, 0.7);
    border-bottom: 1px solid rgba(148, 163, 184, 0.15);
  }
  
  .container {
    max-width: 980px;
    margin: 0 auto;
    padding: 0 1rem;
  }
  
  .topbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0.75rem 0;
  }
  
  nav a {
    color: var(--muted);
    text-decoration: none;
    margin: 0 0.5rem;
    font-weight: 600;
    font-size: 0.95rem;
  }
  
  nav a:hover, nav a:focus {
    color: var(--accent);
    outline: none;
  }
  
  .hero {
    padding: 3.5rem 0 2rem;
    display: grid;
    gap: 1.5rem;
  }
  
  .title {
    font-size: clamp(1.75rem, 2.5vw + 1rem, 3rem);
    margin: 0;
  }
  
  .subtitle {
    color: var(--muted);
    margin: 0.25rem 0 0;
  }
  
  .card {
    background: linear-gradient(180deg, rgba(255,255,255,0.02), rgba(255,255,255,0.01));
    border: 1px solid rgba(148, 163, 184, 0.15);
    border-radius: 16px;
    padding: 1.25rem;
    box-shadow: 0 10px 30px rgba(0,0,0,0.25);
  }
  
  .grid { display: grid; gap: 1rem; }
  
  @media (min-width: 768px) {
    .grid-2 { grid-template-columns: 1fr 1fr; }
    .grid-3 { grid-template-columns: repeat(3, 1fr); }
  }
  
  h2 {
    margin-top: 1rem;
    border-left: 4px solid var(--accent);
    padding-left: 0.5rem;
  }
  
  h3 { margin-top: 0.5rem; color: var(--accent-2); }
  
  ul { padding-left: 1.2rem; }
  
  a.link { color: var(--accent); }
  
  figure { margin: 0; }
  
  figcaption {
    color: var(--muted);
    font-size: 0.9rem;
    margin-top: 0.35rem;
  }
  
  table { width: 100%; border-collapse: collapse; }
  
  th, td {
    border-bottom: 1px solid rgba(148,163,184,0.2);
    padding: 0.6rem;
    text-align: left;
  }
  
  th { color: var(--accent-2); }
  
  footer {
    margin-top: 2rem;
    color: var(--muted);
    border-top: 1px solid rgba(148,163,184,0.15);
    padding: 1rem 0 2rem;
    font-size: 0.95rem;
  }
  
  /* Modo de impressão (para entregar na escola) */
  @media print {
    header, .hero, nav, .no-print { display: none !important; }
    body { background: white; color: black; }
    .card { border: none; box-shadow: none; }
    h2 { border-left-color: black; }
    a { color: black; text-decoration: none; }
  }