Hi Guan_Yee
There’s a bunch of things I see in your code that don’t really make sense to me so can you describe what your trying to do in the App ?
In the bottom container your creating a separate widget (?) and adding a horizontal layout to it. The horizontal will center automatically for you so you don’t need to set alignment. You can set spacing or margins for that layout to achieve the display you want. Might be way easier to attach layouts to your main screen instead of separate widgets but I’m guessing since I’m not 100% sure what your trying to achieve.
Coloring can be changed by using the setStyleSheet for the widget or application level to set multiple widgets (using CSS, see Styling widgets for more info).