#nexus-sign-form {
  max-width: 700px;
  margin: 0 auto;
  background: #fff;
  padding: 20px;
  border-radius: 8px;
  box-shadow: 0 0 15px rgba(0,0,0,0.1);
}

canvas {
  background: #fafafa;
  cursor: crosshair;
}
button {
  margin-top: 10px;
}