<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100">
  <!-- Dark background -->
  <rect width="100" height="100" fill="#0a0a1a"/>
  
  <!-- Cyan square with rounded corners -->
  <rect x="12" y="12" width="76" height="76" rx="10" fill="#00d9ff"/>
  
  <!-- White S -->
  <text x="50" y="68" font-family="Arial, sans-serif" font-size="65" font-weight="bold" fill="white" text-anchor="middle">S</text>
</svg>