It’s the user who’s mobile, moreso than the device, and users will turn to the best screen available when they want to get things done. Will your product work on that screen, whatever size, shape, or capabilities it offers?
Can a single information architecture serve multiple device types? How do you design simultaneously for portrait and landscape orientations, and multiple device types, sizes, and screen resolutions? How are digital experiences like products and how are they like services?
And how do you design experiences for users that may be moving from device to device and moving their data from app to app from one person to another?