* { box-sizing: border-box; }
html, body {
  margin: 0; height: 100%;
  background: #0b0f17; color: #f3f4f6;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
  overflow: hidden;
}
#sim-app { position: relative; width: 100vw; height: 100vh; }
#viewport-container { position: absolute; inset: 0; cursor: crosshair; }
#viewport-container canvas { display: block; }
button { font: inherit; }
.hidden { display: none !important; }