window.WSPrint = {
  setMode(mode){ // mode: "student" | "teacher" | "teacher_preview"
    document.documentElement.classList.toggle("ws-teacher", mode !== "student");
    document.documentElement.classList.toggle("ws-preview", mode === "teacher_preview");
  },
  print(){ setTimeout(()=>window.print(), 60); }
};

.wsWatermark{
  display:none;
  position:fixed;
  inset:0;
  pointer-events:none;
  z-index:999999;
  opacity:.10;
  font-weight:900;
  font-size:72px;
  letter-spacing:.12em;
  transform:rotate(-18deg);
  align-items:center;
  justify-content:center;
}
html.ws-preview .wsWatermark{ display:flex; }

@media print{
  html.ws-preview .wsWatermark{ display:flex; }
}