body {
  font-family: sans-serif;
  overflow: hidden;
  display: flex;
  justify-content: center;
  align-items: center;
  --bodymargin : 1px;
  --wContent: calc(100vw - 0.01*var(--bodymargin));
  --hContent: calc(100vh - 0.01*var(--bodymargin));
  margin: 0;
  padding: 0;
  height: 100vh;
  image-rendering: auto;
  font-size: 0;
}

#cw
{
  display : inline-block;
}

svg{
  display : inline-block;
}

#cw canvas
{
  max-width: var(--wContent);
  max-height: var(--hContent);
}