Terrible hack for HaxeFlixel that adds a separation (collision) function for circle-shaped hitboxes... it's a hack, so it just assumes a circular collider of radius = width/2 ... plug this into a custom FlxG.overlap collision call in your main PlayState... also I don't know how to code so sorry lol

FlxSeparateCircle.hx

public static function separateCircle(circle1:FlxSprite, circle2:FlxSprite):Bool
{
  var totalRadius:Float = circle1.width / 2 + circle2.width / 2;
  var c1 = circle1.getMidpoint(FlxPoint.weak());
  var c2 = circle2.getMidpoint(FlxPoint.weak());
  var distanceSquared:Float = (c1.x - c2.x) * (c1.x - c2.x) + (c1.y - c2.y) * (c1.y - c2.y);

  if (distanceSquared < totalRadius * totalRadius)
  {
    var overlap:Float = totalRadius - Math.sqrt(distanceSquared);
    var normal = FlxVector.get(c1.x - c2.x, c1.y - c2.y).normalize().scale(overlap);
    circle1.setPosition(circle1.x + normal.x, circle1.y + normal.y);

    c1.putWeak();
    c2.putWeak();
    normal.put();
    return true;
  }

  c1.putWeak();
  c2.putWeak();
  return false;
}