In this project the GridView has been misused.
- The root of the visual tree must use an `AppUI.UI.Panel` visual element.
- The theme stylesheet used on the PanelSettings asset must use one of the provided by App UI (such as `App UI.tss`).
- You should not hack the layout of the GridView (like changing the flex-direction of its content container) as it has been built to handle the layout of items.
- App UI has been built to be pixel perfect no matter the physical size of the screen. It is highly recommended to use the `Constant Physical Size` Scale Mode in the PanelSettings asset. This way the layout of components will scale correctly based on a 96dpi DPI reference. After that you can set your GameView aspect ratio to `Free aspect` and disable `Low-resolution Aspect Ratios`.
Information about how to use App UI components is available in the package documentation:
https://docs.unity3d.com/Packages/com.unity.dt.app-ui@2.2/manual/index.html