uses GraphABC;
const
  RndMax = 255;
  
type
  Point3D = class
    X, Y, Z: real;
    
    constructor(px, py, pz: real);
    begin
      X := px;
      Y := py;
      Z := pz;
    end;
  end;

procedure Draw(pA, pC: Point3D; bZ, dZ: real);
begin
  var pB := new Point3D(pC.X, pA.Y, bZ);
  var pD := new Point3D(pA.X, pC.Y, dZ);
  
  var cx := (pA.X + pB.X) / 2;
  var cy := (pB.Y + pC.Y) / 2;
  
  if (pB.X - pA.X) * (pC.Y - pB.Y) > 1 then
  begin
    var maxz := Max(Max(Max(pA.Z, pB.Z), pC.Z), pD.Z);
    var minz := Min(Min(Min(pA.Z, pB.Z), pC.Z), pD.Z);
    
    var randz := 0.0;
    if maxz - minz > 0 then randz := minz + Random() * (maxz - minz);
    var pCenter := new Point3D(cx, cy, randz);
    
    var p1 := new Point3D(cx, pA.Y, (pA.Z + pB.Z) / 2);
    var p2 := new Point3D(pB.X, cy, (pB.Z + pC.Z) / 2);
    var p3 := new Point3D(cx, pC.Y, (pC.Z + pD.Z) / 2);
    var p4 := new Point3D(pA.X, cy, (pD.Z + pA.Z) / 2);
    
    Draw(pA, pCenter, p1.Z, p4.Z);
    Draw(p1, p2, pB.Z, pCenter.Z);
    Draw(pCenter, pC, p2.Z, p3.Z);
    Draw(p4, p3, pCenter.Z, pD.Z);
  end
  else
  begin
    var zv := Round((pA.Z + pB.Z + pC.Z + pD.Z) / 4);
    SetBrushColor(RGB(0, zv, 255));
    FillRect(Round(pA.X), Round(pA.Y), Round(pC.X), Round(pC.Y));
  end;
end;

begin
  var W := Window.Width;
  var H := Window.Height;
  
  SetWindowIsFixedSize(true);
  
  LockDrawing();
  Draw(new Point3D(0, 0, Random(RndMax)), new Point3D(W, H, Random(RndMax)), Random(RndMax), Random(RndMax));
  Redraw();
end.