Are you using a grid panel? Or are they all on a canvas?
If you want to know if it’s working in the editor, you can’t just have a static screen. There should be a double arrow on the bottom right angled at 45 degrees. Click on that and drag it around. Does your screen scale properly? Drop it back on the screen size you were using when done testing.
Even if you’re using a grid panel, not sure how you’re drawing the black background. I’d probably use a Border widget.