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

html {
  -webkit-text-size-adjust: 100%;
  scroll-padding-top: calc(var(--header-h) + env(safe-area-inset-top, 0px) + var(--space-4));
}

body {
  margin: 0;
  min-height: 100vh;
  background: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: 1rem;
  line-height: 1.55;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

img { display: block; max-width: 100%; height: auto; }
h1, h2, h3, p { margin: 0; }
button, input { font: inherit; color: inherit; }
[hidden] { display: none !important; }

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

:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 3px;
}

.screen {
  min-height: calc(100vh - var(--header-h) - env(safe-area-inset-top, 0px));
  scroll-margin-top: calc(var(--header-h) + env(safe-area-inset-top, 0px) + var(--space-4));
}
/* Títulos: serifa */
h1, h2, h3, .question__title { font-family: var(--font-heading); font-weight: 400; }
.screen:focus { outline: none; }
.screen__title:focus { outline: none; }

.container {
  width: 100%;
  max-width: var(--content-max);
  margin-inline: auto;
  padding-inline: var(--space-5);
}

/* Botón de marca */
.btn {
  position: relative;
  isolation: isolate;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  min-height: 52px;
  min-width: var(--tap-min);
  padding: 0 var(--space-6);
  border: 1px solid var(--color-silver);
  border-radius: var(--radius-sm);
  background: transparent;
  color: var(--color-text);
  font-weight: 600;
  font-size: 0.9375rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  cursor: pointer;
  overflow: hidden;
  -webkit-tap-highlight-color: transparent;
  transition: transform var(--motion-fast) var(--ease-out);
}
/* Relleno: se anima por opacity, no por background */
.btn::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: -1;
  background: var(--color-silver);
  opacity: 0;
  transition: opacity var(--motion-fast) var(--ease-out);
}
.btn:hover::before { opacity: 0.14; }
.btn:active { transform: scale(0.97); }
.btn:active::before { opacity: 0.28; }

.btn--primary { background: var(--color-text); color: #0a0b0d; border-color: var(--color-text); }
.btn--primary::before { background: var(--color-accent); }
.btn--primary:hover::before { opacity: 0.22; }
.btn--primary:active::before { opacity: 0.4; }

.btn--ghost { border-color: var(--color-line-soft); }

.btn[disabled] { cursor: progress; }

/* Reduced motion: se elimina el desplazamiento y la escala; el feedback queda en opacity/color */
@media (prefers-reduced-motion: reduce) {
  .btn { transition: none; }
  .btn:active { transform: none; }
}

@media (min-width: 768px) {
  .btn { min-height: 56px; }
}

@media (min-width: 1024px) {
  .container { padding-inline: var(--space-7); }
  .btn { transition: transform var(--motion-fast) var(--ease-out), box-shadow var(--motion-medium) var(--ease-out); }
  .btn--primary:hover { box-shadow: 0 8px 28px -10px rgba(0, 173, 239, 0.55); }
  .btn--ghost:hover { border-color: var(--color-silver); }
}
@media (min-width: 1024px) and (prefers-reduced-motion: reduce) {
  .btn { transition: none; }
}