color {
  bounds: 40 40 70 70;
  color: transparent;
}

clip {
  clip: 50 50 50 50;
  child: opacity {
    opacity: 0.4;
    child: rounded-clip {
      clip: 50 50 100 100 / 50;
      child: color {
        bounds: 50 50 100 100;
        color: red;
      }
    }
  }
}

debug {
  message: "clipped out area";
  child: container {
    color {
      bounds: 50 70 10 30;
      color: black;
    }
    color {
      bounds: 55 55 20 20;
      color: black;
    }
    color {
      bounds: 70 50 30 10;
      color: black;
    }
  }
}