/* ==========================================================================
   Generador de códigos QR — sistema visual
   --------------------------------------------------------------------------
   Dirección: oscuro elegante, glass sobrio, mucho aire, micro-animación.
   Estructura del fichero:
     1. Tokens            6. Presets
     2. Base y utilidades 7. Preview y avisos
     3. Cabecera          8. Toast y footer
     4. Layout/secciones  9. Movimiento reducido
     5. Controles
   ========================================================================== */

/* ==========================================================================
   1. Tokens
   ========================================================================== */
:root {
  /* --- Capas de fondo: nunca negro puro --- */
  --bg: #0e1015;
  --bg-elevated: #14161d;
  --surface: rgba(255, 255, 255, .045);
  --surface-strong: rgba(255, 255, 255, .07);
  --surface-solid: #171a22;        /* fallback sin backdrop-filter */
  --surface-input: rgba(255, 255, 255, .04);

  /* --- Bordes --- */
  --border: rgba(255, 255, 255, .07);
  --border-strong: rgba(255, 255, 255, .12);
  --border-hover: rgba(255, 255, 255, .18);

  /* --- Texto --- */
  --text: #eef0f6;
  --text-soft: #b3b9c9;
  --text-muted: #858c9e;

  /* --- Acento único --- */
  --accent: #6c72ff;
  --accent-hover: #7d83ff;
  --accent-soft: rgba(108, 114, 255, .16);
  --accent-ring: rgba(108, 114, 255, .38);
  --accent-glow: rgba(108, 114, 255, .30);
  --on-accent: #ffffff;

  /* --- Semánticos --- */
  --ok: #34d399;
  --ok-soft: rgba(52, 211, 153, .13);
  --ok-border: rgba(52, 211, 153, .32);
  --warn: #fbbf24;
  --warn-soft: rgba(251, 191, 36, .12);
  --warn-border: rgba(251, 191, 36, .30);
  --danger: #f87171;
  --danger-soft: rgba(248, 113, 113, .12);
  --danger-border: rgba(248, 113, 113, .32);
  --info: #7dd3fc;
  --info-soft: rgba(125, 211, 252, .11);
  --info-border: rgba(125, 211, 252, .28);

  /* --- Espaciado (escala de 4) --- */
  --sp-1: .25rem;  --sp-2: .5rem;   --sp-3: .75rem;  --sp-4: 1rem;
  --sp-5: 1.25rem; --sp-6: 1.5rem;  --sp-8: 2rem;    --sp-10: 2.75rem;

  /* --- Radios --- */
  --r-card: 16px;
  --r-panel: 12px;
  --r-input: 10px;
  --r-sm: 8px;
  --r-pill: 999px;

  /* --- Sombras: suaves y difusas --- */
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, .28);
  --shadow: 0 4px 12px rgba(0, 0, 0, .26), 0 16px 40px rgba(0, 0, 0, .28);
  --shadow-lift: 0 6px 18px rgba(0, 0, 0, .32), 0 22px 56px rgba(0, 0, 0, .34);
  --shadow-accent: 0 8px 26px rgba(108, 114, 255, .34);

  /* --- Glass --- */
  --blur: blur(14px) saturate(150%);
  --blur-sm: blur(8px) saturate(140%);

  /* --- Movimiento --- */
  --ease: cubic-bezier(.22, .61, .36, 1);
  --t-fast: 100ms;
  --t-base: 160ms;
  --t-slow: 240ms;

  /* --- Tipografía --- */
  --font: system-ui, -apple-system, "SF Pro Text", "Segoe UI", Roboto,
          "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas,
          "Liberation Mono", monospace;
}

/* ==========================================================================
   2. Base y utilidades
   ========================================================================== */
*, *::before, *::after { box-sizing: border-box; }

html {
  -webkit-text-size-adjust: 100%;
  color-scheme: dark;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font);
  font-size: 15px;
  line-height: 1.6;
  color: var(--text);
  background-color: var(--bg);
  /* Dos halos muy difusos: dan profundidad sin ensuciar. */
  background-image:
    radial-gradient(60rem 32rem at 12% -8%, rgba(108, 114, 255, .13), transparent 62%),
    radial-gradient(48rem 28rem at 96% 4%, rgba(52, 211, 153, .07), transparent 60%);
  background-attachment: fixed;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

h1, h2, h3 { line-height: 1.25; letter-spacing: -.011em; margin: 0; }

a {
  color: var(--text-soft);
  text-decoration-color: var(--border-strong);
  text-underline-offset: 3px;
  transition: color var(--t-fast) var(--ease);
}
a:hover { color: var(--text); }

/* Foco: anillo de acento, nunca un outline duro. */
:focus-visible {
  outline: none;
  box-shadow: 0 0 0 3px var(--accent-ring);
  border-radius: var(--r-sm);
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  z-index: 100;
  padding: var(--sp-3) var(--sp-4);
  background: var(--accent);
  color: var(--on-accent);
  font-weight: 600;
  border-radius: 0 0 var(--r-panel) 0;
}
.skip-link:focus { left: 0; }

/* Superficie glass reutilizable. */
.glass {
  background: var(--surface);
  border: 1px solid var(--border);
  -webkit-backdrop-filter: var(--blur);
  backdrop-filter: var(--blur);
}
/* Sin backdrop-filter (Firefox antiguo, etc.): superficie sólida equivalente. */
@supports not ((backdrop-filter: blur(1px)) or (-webkit-backdrop-filter: blur(1px))) {
  .glass, .section, .preview-card, .toast, .mode-switch, .preset {
    background: var(--surface-solid);
  }
}

/* ==========================================================================
   3. Cabecera
   ========================================================================== */
.topbar {
  position: relative;
  border-bottom: 1px solid var(--border);
  background: rgba(14, 16, 21, .62);
  -webkit-backdrop-filter: var(--blur);
  backdrop-filter: var(--blur);
}

.topbar__inner {
  max-width: 1280px;
  margin: 0 auto;
  padding: var(--sp-5) var(--sp-6);
}

.topbar__row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--sp-4);
  flex-wrap: wrap;
}

.topbar__title {
  display: flex;
  align-items: center;
  gap: var(--sp-3);
  font-size: 1.22rem;
  font-weight: 640;
  letter-spacing: -.02em;
}

.topbar__logo {
  display: grid;
  place-items: center;
  width: 2rem;
  height: 2rem;
  border-radius: var(--r-sm);
  font-family: var(--mono);
  font-size: .95rem;
  letter-spacing: -.12em;
  color: var(--on-accent);
  background: linear-gradient(140deg, var(--accent), #9b5cf6);
  box-shadow: var(--shadow-accent);
}

.topbar__claim {
  margin: var(--sp-2) 0 0;
  font-size: .85rem;
  color: var(--text-muted);
}

/* --- Segmented control con pastilla deslizante --- */
.mode-switch {
  position: relative;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0;
  padding: 3px;
  border-radius: var(--r-pill);
  background: var(--surface);
  border: 1px solid var(--border);
  -webkit-backdrop-filter: var(--blur-sm);
  backdrop-filter: var(--blur-sm);
}

.mode-switch input[type="radio"] {
  position: absolute;
  width: 1px; height: 1px;
  margin: -1px; padding: 0; border: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  clip-path: inset(50%);
  white-space: nowrap;
}

.mode-switch label {
  position: relative;
  z-index: 1;
  min-width: 5.6rem;
  padding: .34rem .95rem;
  border-radius: var(--r-pill);
  text-align: center;
  font-size: .83rem;
  font-weight: 600;
  color: var(--text-muted);
  cursor: pointer;
  user-select: none;
  transition: color var(--t-base) var(--ease);
}
.mode-switch input:checked + label { color: var(--text); }

.mode-switch__pill {
  position: absolute;
  z-index: 0;
  top: 3px;
  left: 3px;
  width: calc(50% - 3px);
  height: calc(100% - 6px);
  border-radius: var(--r-pill);
  background: var(--accent);
  box-shadow: var(--shadow-accent);
  transition: transform var(--t-slow) var(--ease);
}
body[data-mode="advanced"] .mode-switch__pill { transform: translateX(100%); }

.mode-switch input:focus-visible + label {
  box-shadow: 0 0 0 3px var(--accent-ring);
}

/* ==========================================================================
   4. Layout y secciones
   ========================================================================== */
.layout {
  max-width: 1280px;
  margin: 0 auto;
  padding: var(--sp-8) var(--sp-6) var(--sp-10);
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 420px);
  gap: var(--sp-6);
  align-items: start;
}

.layout__controls {
  display: flex;
  flex-direction: column;
  gap: var(--sp-5);
  min-width: 0;
}

.layout__preview {
  position: sticky;
  top: var(--sp-6);
  min-width: 0;
  isolation: isolate;
}

@media (max-width: 960px) {
  .layout {
    grid-template-columns: minmax(0, 1fr);
    padding: var(--sp-6) var(--sp-4) var(--sp-8);
  }
  .layout__preview { order: -1; position: static; }
  .topbar__inner { padding: var(--sp-4); }
}

.section {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--r-card);
  box-shadow: var(--shadow);
  -webkit-backdrop-filter: var(--blur);
  backdrop-filter: var(--blur);
  overflow: hidden;
}

.section__head { font-size: 1rem; }

.section__toggle {
  width: 100%;
  display: flex;
  align-items: center;
  gap: var(--sp-3);
  padding: var(--sp-5) var(--sp-5);
  background: none;
  border: 0;
  font: inherit;
  font-weight: 620;
  letter-spacing: -.01em;
  color: var(--text);
  text-align: left;
  cursor: pointer;
  transition: background var(--t-fast) var(--ease);
}
.section__toggle:hover:not(:disabled) { background: rgba(255, 255, 255, .03); }

.section__icon {
  flex: none;
  width: 1.4rem;
  height: 1.4rem;
  display: grid;
  place-items: center;
  border-radius: var(--r-sm);
  background: var(--accent-soft);
  color: #b6baff;
  font-size: .72rem;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
}

.section__chevron {
  flex: none;
  width: .45rem;
  height: .45rem;
  border-right: 1.8px solid var(--text-muted);
  border-bottom: 1.8px solid var(--text-muted);
  transform: rotate(45deg);
  transition: transform var(--t-slow) var(--ease);
}
.section__toggle[aria-expanded="false"] .section__chevron { transform: rotate(-45deg); }

.section__body {
  padding: 0 var(--sp-5) var(--sp-5);
  border-top: 1px solid var(--border);
}

/* Al desplegar, el panel entra con altura y opacidad. Al plegar es inmediato:
   el atributo `hidden` es el contrato de accesibilidad y no se toca. */
.section__body:not([hidden]) {
  animation: panel-in var(--t-slow) var(--ease);
}
@keyframes panel-in {
  from { opacity: 0; max-height: 0; transform: translateY(-4px); }
  to   { opacity: 1; max-height: 240vh; transform: none; }
}

.subhead {
  margin: var(--sp-6) 0 var(--sp-2);
  font-size: .72rem;
  font-weight: 650;
  text-transform: uppercase;
  letter-spacing: .09em;
  color: var(--text-muted);
}

.rule {
  border: 0;
  border-top: 1px solid var(--border);
  margin: var(--sp-6) 0;
}

/* ==========================================================================
   5. Controles
   ========================================================================== */
.field { margin-top: var(--sp-5); }
.field:first-child { margin-top: var(--sp-5); }

.field > label,
.label-row > label {
  display: block;
  margin-bottom: var(--sp-2);
  font-size: .84rem;
  font-weight: 560;
  color: var(--text-soft);
}

.label-row {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--sp-2);
  margin-bottom: var(--sp-2);
}
.label-row > label { margin-bottom: 0; }

.mirror {
  font-family: var(--mono);
  font-size: .74rem;
  font-variant-numeric: tabular-nums;
  color: var(--text-muted);
  background: var(--surface-input);
  border: 1px solid var(--border);
  border-radius: var(--r-sm);
  padding: .1rem .45rem;
  white-space: nowrap;
}
.mirror--hex { text-transform: lowercase; }

input[type="text"], input[type="url"], input[type="tel"], input[type="email"],
input[type="number"], input[type="date"], input[type="datetime-local"],
select, textarea {
  width: 100%;
  padding: .58rem .7rem;
  font: inherit;
  font-size: .9rem;
  color: var(--text);
  background: var(--surface-input);
  border: 1px solid var(--border-strong);
  border-radius: var(--r-input);
  transition: border-color var(--t-fast) var(--ease),
              background var(--t-fast) var(--ease),
              box-shadow var(--t-fast) var(--ease);
}
input:hover:not(:disabled), select:hover:not(:disabled), textarea:hover {
  border-color: var(--border-hover);
  background: var(--surface-strong);
}
input:focus, select:focus, textarea:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-ring);
}

select {
  appearance: none;
  padding-right: 2.1rem;
  background-image:
    linear-gradient(45deg, transparent 50%, var(--text-muted) 50%),
    linear-gradient(135deg, var(--text-muted) 50%, transparent 50%);
  background-position: calc(100% - 1.05rem) 55%, calc(100% - .75rem) 55%;
  background-size: 5px 5px, 5px 5px;
  background-repeat: no-repeat;
}

textarea { resize: vertical; min-height: 4.5rem; }

input[type="file"] {
  width: 100%;
  font-size: .84rem;
  color: var(--text-muted);
}
input[type="file"]::file-selector-button {
  margin-right: var(--sp-3);
  padding: .4rem .8rem;
  font: inherit;
  font-size: .82rem;
  font-weight: 600;
  color: var(--text);
  background: var(--surface-strong);
  border: 1px solid var(--border-strong);
  border-radius: var(--r-sm);
  cursor: pointer;
  transition: border-color var(--t-fast) var(--ease);
}
input[type="file"]::file-selector-button:hover { border-color: var(--border-hover); }

/* --- Color: swatch grande + hex --- */
.color-row {
  display: flex;
  align-items: center;
  gap: var(--sp-3);
}

input[type="color"] {
  flex: 0 0 5.5rem;
  height: 2.7rem;
  padding: 4px;
  background: var(--surface-input);
  border: 1px solid var(--border-strong);
  border-radius: var(--r-input);
  cursor: pointer;
  transition: border-color var(--t-fast) var(--ease), box-shadow var(--t-fast) var(--ease);
}
input[type="color"]:hover { border-color: var(--border-hover); }
input[type="color"]::-webkit-color-swatch-wrapper { padding: 0; }
input[type="color"]::-webkit-color-swatch { border: none; border-radius: 6px; }
input[type="color"]::-moz-color-swatch { border: none; border-radius: 6px; }
.color-row .mirror { flex: none; padding: .32rem .6rem; font-size: .8rem; }

/* --- Sliders --- */
input[type="range"] {
  width: 100%;
  appearance: none;
  height: 1.5rem;
  background: transparent;
  cursor: pointer;
}
input[type="range"]::-webkit-slider-runnable-track {
  height: 5px;
  border-radius: var(--r-pill);
  background: var(--surface-strong);
  border: 1px solid var(--border);
}
input[type="range"]::-webkit-slider-thumb {
  appearance: none;
  margin-top: -6px;
  width: 16px; height: 16px;
  border-radius: 50%;
  background: var(--accent);
  border: 2px solid #fff;
  box-shadow: var(--shadow-sm);
  transition: transform var(--t-fast) var(--ease);
}
input[type="range"]:hover::-webkit-slider-thumb { transform: scale(1.12); }
input[type="range"]:disabled::-webkit-slider-thumb { background: var(--text-muted); border-color: var(--border-strong); }
input[type="range"]::-moz-range-track {
  height: 5px; border-radius: var(--r-pill); background: var(--surface-strong);
}
input[type="range"]::-moz-range-thumb {
  width: 14px; height: 14px; border-radius: 50%;
  background: var(--accent); border: 2px solid #fff;
}
input[type="range"]:disabled { opacity: .55; cursor: not-allowed; }

/* --- Checkbox por defecto --- */
.check-row {
  display: flex;
  align-items: flex-start;
  gap: var(--sp-3);
}
.check-row input[type="checkbox"] {
  margin-top: .2rem;
  width: 1.05rem; height: 1.05rem;
  accent-color: var(--accent);
  flex: none;
}
.check-row label {
  font-size: .86rem;
  font-weight: 500;
  color: var(--text-soft);
  margin: 0;
  cursor: pointer;
}

/* --- Switch tipo iOS: mismo <input type="checkbox">, sólo presentación --- */
.check-row--switch { align-items: center; }

.check-row--switch input[type="checkbox"] {
  appearance: none;
  position: relative;
  margin: 0;
  width: 2.35rem;
  height: 1.35rem;
  border-radius: var(--r-pill);
  background: var(--surface-strong);
  border: 1px solid var(--border-strong);
  cursor: pointer;
  transition: background var(--t-base) var(--ease), border-color var(--t-base) var(--ease);
}
.check-row--switch input[type="checkbox"]::after {
  content: "";
  position: absolute;
  top: 50%;
  left: 2px;
  width: 1.05rem;
  height: 1.05rem;
  border-radius: 50%;
  background: #fff;
  box-shadow: var(--shadow-sm);
  transform: translate(0, -50%);
  transition: transform var(--t-base) var(--ease);
}
.check-row--switch input[type="checkbox"]:checked {
  background: var(--accent);
  border-color: var(--accent);
}
.check-row--switch input[type="checkbox"]:checked::after {
  transform: translate(calc(2.35rem - 1.05rem - 6px), -50%);
}
.check-row--switch input[type="checkbox"]:focus-visible {
  box-shadow: 0 0 0 3px var(--accent-ring);
}

.help {
  margin: var(--sp-2) 0 0;
  font-size: .79rem;
  line-height: 1.5;
  color: var(--text-muted);
}

.error {
  margin: var(--sp-2) 0 0;
  font-size: .79rem;
  color: var(--danger);
  font-weight: 560;
  display: none;
}
.error.is-visible { display: block; }

.is-invalid {
  border-color: var(--danger) !important;
  box-shadow: 0 0 0 3px var(--danger-soft) !important;
}

.payload {
  font-family: var(--mono);
  font-size: .78rem;
  line-height: 1.55;
  white-space: pre;
  overflow-wrap: normal;
  overflow-x: auto;
  color: var(--text-soft);
}

/* --- Editor de gradiente --- */
.gradient-editor {
  margin-top: var(--sp-4);
  padding: var(--sp-4);
  background: rgba(255, 255, 255, .022);
  border: 1px solid var(--border);
  border-radius: var(--r-panel);
}
.gradient-editor .field:first-child { margin-top: var(--sp-4); }
.gradient-body { margin-top: var(--sp-2); }

.stops { margin-top: var(--sp-4); }

.stop-row {
  display: grid;
  grid-template-columns: 3.2rem 1fr auto auto;
  align-items: center;
  gap: var(--sp-3);
  margin-bottom: var(--sp-3);
}
.stop-row input[type="color"] { height: 2.1rem; padding: 3px; }

/* --- Botones --- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--sp-2);
  padding: .6rem 1rem;
  font: inherit;
  font-size: .88rem;
  font-weight: 600;
  color: var(--text);
  background: var(--surface-strong);
  border: 1px solid var(--border-strong);
  border-radius: var(--r-input);
  cursor: pointer;
  text-align: center;
  transition: background var(--t-fast) var(--ease),
              border-color var(--t-fast) var(--ease),
              transform var(--t-fast) var(--ease),
              box-shadow var(--t-base) var(--ease);
}
.btn:hover:not(:disabled) { border-color: var(--border-hover); background: rgba(255, 255, 255, .09); }
.btn:active:not(:disabled) { transform: translateY(1px); }
.btn:disabled { opacity: .45; cursor: not-allowed; }

.btn--primary {
  background: var(--accent);
  border-color: transparent;
  color: var(--on-accent);
  box-shadow: var(--shadow-accent);
}
.btn--primary:hover:not(:disabled) {
  background: var(--accent-hover);
  transform: translateY(-1px);
  box-shadow: 0 10px 30px rgba(108, 114, 255, .42);
}
.btn--primary:active:not(:disabled) { transform: translateY(0); }

/* Check verde al terminar una descarga. */
.btn--primary.is-done {
  background: var(--ok);
  box-shadow: 0 8px 26px rgba(52, 211, 153, .34);
}
.btn__check {
  display: inline-block;
  animation: check-pop 300ms var(--ease);
}
@keyframes check-pop {
  0%   { transform: scale(.4); opacity: 0; }
  60%  { transform: scale(1.15); opacity: 1; }
  100% { transform: scale(1); opacity: 1; }
}

.btn--danger { background: transparent; border-color: var(--danger-border); color: var(--danger); }
.btn--danger:hover:not(:disabled) { background: var(--danger-soft); border-color: var(--danger); }

.btn--ghost { background: transparent; border-color: var(--border); }
.btn--sm { padding: .3rem .65rem; font-size: .78rem; }
.btn--block { width: 100%; margin-top: var(--sp-5); padding: .72rem 1rem; }
.btn--icon { padding: .3rem .55rem; line-height: 1; color: var(--text-muted); }
.btn--icon:hover:not(:disabled) { color: var(--text); }

.btn-row {
  display: flex;
  flex-wrap: wrap;
  gap: var(--sp-3);
  margin-top: var(--sp-4);
}
.btn-row .btn { flex: 1 1 11rem; background: transparent; }
.btn-row .btn:hover:not(:disabled) { background: var(--surface-strong); }

.btn--file { position: relative; overflow: hidden; }
.btn--file input[type="file"] {
  position: absolute;
  inset: 0;
  opacity: 0;
  width: 100%; height: 100%;
  cursor: pointer;
}
.btn--file:focus-within { box-shadow: 0 0 0 3px var(--accent-ring); }

/* --- Logo --- */
.logo-status {
  display: flex;
  align-items: center;
  gap: var(--sp-3);
  margin-top: var(--sp-4);
  padding: var(--sp-3);
  background: rgba(255, 255, 255, .022);
  border: 1px solid var(--border);
  border-radius: var(--r-panel);
  flex-wrap: wrap;
}
.logo-thumb {
  width: 42px; height: 42px;
  object-fit: contain;
  background: var(--surface-strong);
  border: 1px solid var(--border);
  border-radius: var(--r-sm);
  padding: 4px;
}
.logo-status .help { margin: 0; flex: 1 1 7rem; }

/* ==========================================================================
   6. Presets
   ========================================================================== */
.section--presets { padding: var(--sp-5); }

.presets__title {
  font-size: .72rem;
  font-weight: 650;
  text-transform: uppercase;
  letter-spacing: .09em;
  color: var(--text-muted);
}
.presets__hint {
  margin: var(--sp-1) 0 var(--sp-4);
  font-size: .79rem;
  color: var(--text-muted);
}

.presets {
  display: flex;
  gap: var(--sp-3);
  overflow-x: auto;
  padding-bottom: var(--sp-2);
  scrollbar-width: thin;
  scroll-snap-type: x proximity;
}
.presets::-webkit-scrollbar { height: 6px; }
.presets::-webkit-scrollbar-thumb { background: var(--border-strong); border-radius: var(--r-pill); }

.preset {
  position: relative;
  flex: 0 0 auto;
  scroll-snap-align: start;
  width: 5.05rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--sp-2);
  padding: var(--sp-3) var(--sp-2);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--r-panel);
  font: inherit;
  color: var(--text-soft);
  cursor: pointer;
  transition: border-color var(--t-fast) var(--ease),
              transform var(--t-fast) var(--ease),
              background var(--t-fast) var(--ease);
}
.preset:hover {
  border-color: var(--border-hover);
  background: var(--surface-strong);
  transform: translateY(-2px);
}
.preset:active { transform: translateY(0); }

.preset__thumb {
  width: 56px; height: 56px;
  border-radius: var(--r-sm);
  overflow: hidden;
  display: grid;
  place-items: center;
  background: var(--surface-strong);
}
.preset__thumb canvas, .preset__thumb svg {
  display: block;
  width: 100%; height: 100%;
}

.preset__name {
  font-size: .73rem;
  font-weight: 560;
  text-align: center;
  line-height: 1.25;
}

/* Feedback "aplicado": marca sutil, 900 ms. */
.preset.is-applied {
  border-color: var(--ok-border);
  background: var(--ok-soft);
}
.preset__applied {
  position: absolute;
  top: 6px; right: 6px;
  width: 1.05rem; height: 1.05rem;
  display: grid;
  place-items: center;
  border-radius: 50%;
  background: var(--ok);
  color: #06281c;
  font-size: .62rem;
  font-weight: 800;
  opacity: 0;
  transform: scale(.5);
}
.preset.is-applied .preset__applied {
  animation: check-pop 300ms var(--ease) forwards;
}

/* ==========================================================================
   6b. Modo Básico / Avanzado
   --------------------------------------------------------------------------
   El HTML es único: cada bloque se etiqueta con data-mode y el modo activo vive
   en <body data-mode="…">. Se oculta por CSS (no con el atributo `hidden`) para
   no chocar con las dependencias de UI, que sí usan `hidden`.
   ========================================================================== */

body[data-mode="basic"] [data-mode="advanced"],
body[data-mode="advanced"] [data-mode="basic"] {
  display: none !important;
}

/* En básico las secciones no se pliegan: el encabezado es sólo un título. */
body[data-mode="basic"] .section__chevron,
body[data-mode="basic"] .section__icon {
  display: none;
}

body[data-mode="basic"] .section__toggle {
  cursor: default;
  padding-bottom: var(--sp-3);
  font-size: .72rem;
  font-weight: 650;
  text-transform: uppercase;
  letter-spacing: .09em;
  color: var(--text-muted);
}
body[data-mode="basic"] .section__toggle:disabled { opacity: 1; }
body[data-mode="basic"] .section__body { border-top: 0; padding-top: 0; }

/* ==========================================================================
   7. Preview y avisos
   ========================================================================== */
.preview-card {
  position: relative;
  padding: var(--sp-5);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--r-card);
  box-shadow: var(--shadow-lift);
  -webkit-backdrop-filter: var(--blur);
  backdrop-filter: var(--blur);
}

.layout__preview { position: sticky; }

/* Glow de acento detrás de la tarjeta. Va en el contenedor y no en la propia
   tarjeta: `backdrop-filter` crea contexto de apilamiento y encerraría el
   pseudo-elemento dentro del glass. */
.layout__preview::before {
  content: "";
  position: absolute;
  inset: 6% 4% auto;
  height: 58%;
  border-radius: 50%;
  background: var(--accent-glow);
  filter: blur(64px);
  opacity: .8;
  z-index: 0;
  pointer-events: none;
}
.preview-card { z-index: 1; }

.preview-card__title {
  margin-bottom: var(--sp-4);
  font-size: .72rem;
  font-weight: 650;
  text-transform: uppercase;
  letter-spacing: .09em;
  color: var(--text-muted);
}

.preview-stage {
  display: grid;
  place-items: center;
  padding: var(--sp-6);
  border-radius: var(--r-panel);
  border: 1px solid var(--border);
  background: var(--surface-strong);
  overflow: auto;
}

/* El tablero SÓLO cuando el fondo del QR es transparente: ahí comunica algo
   real (lo que se verá a través del código). Con un fondo opaco el canvas ya
   pinta su propio color y el tablero únicamente aparecería en el anillo de
   padding, sugiriendo una transparencia que no existe. */
.preview-stage.is-checkered {
  background-color: #ffffff;
  background-image:
    linear-gradient(45deg, #e7eaf1 25%, transparent 25%),
    linear-gradient(-45deg, #e7eaf1 25%, transparent 25%),
    linear-gradient(45deg, transparent 75%, #e7eaf1 75%),
    linear-gradient(-45deg, transparent 75%, #e7eaf1 75%);
  background-size: 18px 18px;
  background-position: 0 0, 0 9px, 9px -9px, -9px 0;
}

.qr-preview { line-height: 0; }
.qr-preview canvas, .qr-preview svg {
  max-width: 100%;
  height: auto;
  display: block;
  border-radius: 4px;
  /* Cada update() inserta un nodo nuevo, así que la animación se repite sola. */
  animation: qr-in 150ms var(--ease);
}
@keyframes qr-in {
  from { opacity: .82; transform: scale(.988); }
  to   { opacity: 1;   transform: scale(1); }
}

.preview-error {
  padding: var(--sp-5);
  color: var(--danger);
  font-size: .86rem;
  font-weight: 560;
  text-align: center;
}

.warnings {
  margin-top: var(--sp-4);
  display: flex;
  flex-direction: column;
  gap: var(--sp-2);
}

.warning {
  display: flex;
  align-items: flex-start;
  gap: var(--sp-3);
  margin: 0;
  padding: var(--sp-3) var(--sp-4);
  font-size: .81rem;
  line-height: 1.5;
  border-radius: var(--r-panel);
  border: 1px solid;
  -webkit-backdrop-filter: var(--blur-sm);
  backdrop-filter: var(--blur-sm);
}
.warning__icon { flex: none; font-weight: 700; line-height: 1.5; }

.warning--warn { background: var(--warn-soft); border-color: var(--warn-border); color: #ffdf9e; }
.warning--info { background: var(--info-soft); border-color: var(--info-border); color: #cfeaff; }
.warning--ok   { background: var(--ok-soft);   border-color: var(--ok-border);   color: #a8f0d1; }

/* ==========================================================================
   8. Toast y footer
   ========================================================================== */
.toast {
  position: fixed;
  left: 50%;
  bottom: var(--sp-6);
  transform: translate(-50%, .75rem);
  max-width: min(92vw, 34rem);
  padding: var(--sp-3) var(--sp-5);
  font-size: .85rem;
  font-weight: 560;
  line-height: 1.5;
  border-radius: var(--r-panel);
  border: 1px solid var(--border-strong);
  background: rgba(23, 26, 34, .88);
  color: var(--text);
  box-shadow: var(--shadow-lift);
  -webkit-backdrop-filter: var(--blur);
  backdrop-filter: var(--blur);
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--t-base) var(--ease), transform var(--t-base) var(--ease);
  z-index: 60;
}
.toast.is-visible { opacity: 1; transform: translate(-50%, 0); }

.toast--ok    { border-color: var(--ok-border);     color: #a8f0d1; }
.toast--error { border-color: var(--danger-border); color: #ffc4c4; }
.toast--warn  { border-color: var(--warn-border);   color: #ffdf9e; }
.toast--info  { border-color: var(--info-border);   color: #cfeaff; }

.footer {
  border-top: 1px solid var(--border);
  padding: var(--sp-6) var(--sp-6) var(--sp-8);
}
.footer p {
  max-width: 1280px;
  margin: 0 auto;
  font-size: .79rem;
  color: var(--text-muted);
}

/* ==========================================================================
   9. Movimiento reducido
   ========================================================================== */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    transition-duration: .01ms !important;
    animation-duration: .01ms !important;
    animation-iteration-count: 1 !important;
    scroll-behavior: auto !important;
  }
  .qr-preview canvas, .qr-preview svg,
  .section__body:not([hidden]) { animation: none !important; }
}