While developing a UWP app, you can quickly see what it would look like on various devices in the XAML design window.
The following screenshot shows the 23" Desktop (1920 x 1080) 100% scale emulator:
The following screenshot shows the 57" HoloLens 2D App (1280 x 720) 150% scale emulator:
You can also run the app in a Simulator rather than on your Local Machine. You can also choose Remote Machine or Device:
Simulator can rotate and change input modes and the screen resolution using the buttons in the toolbar on the right edge of the Simulator window:
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