html, body {
  margin: 0;
  background: #ccc;
}
.viewer {
  max-width: 920px;
  'margin: 0 auto;
  position: relative;
}
canvas {
  width: 100%;
  display: block;
  user-select: none;
  pointer-events: none;
}
/* Watermark */
.wm {
  position: fixed;
  top: 20px;
  left: 50%;
  transform: translateX(-50%);
  opacity: 0.2;
  font: 700 14px/1.2 system-ui;
  color: #fff;
  z-index: 9999;
  pointer-events: none;
}
/* Blocco stampa */
@media print {
  body { display: none !important; }
}