/* Header / Navigation — N1b canonical three-section, frosts on scroll */

.nav {
  position: sticky;
  top: 0;
  z-index: var(--z-sticky);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-lg);
  padding-block: var(--space-md);
  padding-inline: var(--page-gutter);
  background: color-mix(in oklch, var(--color-paper) 88%, transparent);
  backdrop-filter: blur(10px) saturate(140%);
  -webkit-backdrop-filter: blur(10px) saturate(140%);
  border-bottom: 1px solid transparent;
  transition: background-color var(--dur-short) var(--ease-out),
              border-color var(--dur-short) var(--ease-out),
              box-shadow var(--dur-short) var(--ease-out);
}
.nav.is-scrolled {
  background: color-mix(in oklch, var(--color-paper) 97%, transparent);
  border-bottom-color: var(--color-rule);
  box-shadow: var(--shadow-whisper);
}

.nav__wordmark {
  font-family: var(--font-wordmark);
  font-weight: 900;
  font-size: var(--text-md);
  letter-spacing: -0.02em;
  text-transform: uppercase;
  white-space: nowrap;
}

.nav__links {
  display: flex;
  align-items: center;
  gap: var(--space-lg);
}
.nav__links a {
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-ink-2);
  white-space: nowrap;
  padding-block: var(--space-2xs);
  border-bottom: 1px solid transparent;
  transition: color var(--dur-short) var(--ease-out), border-color var(--dur-short) var(--ease-out);
}
.nav__links a:hover { color: var(--color-ink); border-color: var(--color-accent); }

.nav__actions {
  display: flex;
  align-items: center;
  gap: var(--space-md);
}
.nav__student-link {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-ink-2);
  white-space: nowrap;
  display: inline-flex;
  align-items: center;
  gap: var(--space-2xs);
}
.nav__student-link:hover { color: var(--color-accent); }

.nav__toggle {
  display: none;
  min-width: 44px;
  min-height: 44px;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
}
.nav__toggle:hover { background: var(--color-paper-2); }

.nav__sheet {
  display: none;
}

@media (max-width: 60rem) {
  .nav__links { display: none; }
  /* El link de alumno y el botón Inscríbete ya están duplicados en el sheet móvil —
     en la barra colapsada solo debe quedar el disparador del menú. */
  .nav__actions > .nav__student-link,
  .nav__actions > .btn--accent { display: none; }
  .nav__toggle { display: inline-flex; }

  .nav__sheet {
    position: fixed;
    inset: 0;
    top: 0;
    z-index: var(--z-modal);
    background: var(--color-paper);
    padding: var(--space-md) var(--page-gutter) var(--space-2xl);
    display: none;
    flex-direction: column;
    gap: var(--space-2xl);
  }
  .nav__sheet.is-open { display: flex; }

  .nav__sheet-top {
    display: flex;
    align-items: center;
    justify-content: space-between;
  }
  .nav__sheet-links {
    display: flex;
    flex-direction: column;
    gap: var(--space-lg);
  }
  .nav__sheet-links a {
    font-family: var(--font-display);
    font-size: var(--text-2xl);
    font-weight: 600;
  }
  .nav__sheet-actions {
    display: flex;
    flex-direction: column;
    gap: var(--space-md);
    margin-top: auto;
  }
  .nav__sheet-actions .btn { width: 100%; justify-content: center; }
}