/* ===== Chart AutoFix: safe defaults (non-invasive) ===== */
#sim-panel { min-height: 300px }
#sim-panel canvas#sim-chart {
  width: 100% !important;
  min-height: 300px;
  height: 300px !important;     /* اگر ارتفاع صفر باشد، Chart.js چیزی نمی‌کشد */
  display: block;
}
@media (max-width: 640px){
  #sim-panel { min-height: 240px }
  #sim-panel canvas#sim-chart { min-height: 240px; height: 240px !important }
}