In this recipe, you added preview packages (UI Toolkit and UI Builder) to your Unity project. You then used UI Builder to create a UXML file describing the elements in your interface – a row containing two buttons. This was saved as a file called ui-1.
UI Toolkit uses a Panel Settings asset file (in the Project window) to record how a UI Panel is to be displayed. So, we created one called PanelSettings1.
To get Unity to display your UI asset in the scene, we had to add a UI Document component to a Scene GameObject. We did this by creating a new, empty GameObject GameUI. Since we want to display clickable buttons, we also needed to add an Input System Event System (UI Toolkit) component to this GameObject. We were then able to link our ui-1 and PanelSettings1 asset files from the Project window to this UI Document component in our GameUI GameObject in the scene.
You then added styling to the buttons (yellow background, larger text...