assets/icon.svg

<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" width="512" height="512">
  <!-- treg composer icon: the ▚ mark, white on black. Same geometry as web/favicon.svg and
       assets/brand/twitter/, recoloured to pure black/white.
       FILLED on purpose: a transparent white mark disappears on a light background, and this
       renders in a host UI whose backdrop we do not control. -->
  <rect width="512" height="512" rx="112" fill="#000000"/>
  <rect x="111" y="111" width="140.5" height="140.5" rx="20" fill="#ffffff"/>
  <rect x="260.5" y="260.5" width="140.5" height="140.5" rx="20" fill="#ffffff"/>
</svg>