Your mobile phone move on the desk when it vibrates? You know when your mobile rings the buzzing makes you jump and it's fun to watch it move across the desk ...
So, set your phone down vertically and as straight as possible, then activate the vibration and tell us which way it turns, left right, up, down or not at all. It's best to do this two or three times in case of flukes.
Mine moves left.
You can select multiple choices if your phone likes to move different ways.