Maintain focus on the primary content in all environments.
Avoid gratuitous changes in layout. A comparable experience in all environments lets people maintain their usage patterns when they rotate a device or run your app on a different device. For example, if you use a grid to display images in a horizontally regular environment, you don’t have to display the same information in a list in a horizontally compact environment, although you might adjust the dimensions of the grid.
Be straightforward if your app runs in only one orientation. People expect to use your app in different orientations, and it’s best when you can fulfill that expectation. But if it’s essential that your app run in only one orientation, you should: