//PascalABC.NET 3.1 сборка 1200
uses GraphABC;
const
    w = 30;
    delay = 12;

begin
    var k := Window.Width / Window.Height;
    Brush.Color := clForestGreen;
    
    for var i := 0 to Window.Height do
    begin
        var p := new System.Drawing.Point(round(k * i), i);
        FillRectangle(p.X, p.Y, p.X + w, p.Y + w);
        Sleep(delay);
        Window.Clear(clYellowGreen);
    end;
    
    for var i := 0 to Window.Height do
    begin
        var p := new System.Drawing.Point(Window.Width - round(k * i), i);
        FillRectangle(p.X - w, p.Y, p.X, p.Y + w);
        Sleep(delay);
        Window.Clear(clYellowGreen);
    end;
end.