in Windows 10, awoke to Screen image upside-down & mouse response mirrored

(I'm a computer novice plus I'm old -- to anyone who can help me, please bear these things in mind.)Here is my issue:  I fell asleep streaming videos and awoke several hours later to find my computer looked as though it had gone to sleep (dark screen).  I clicked the mouse to wake it up, and saw that first my start-up and then my desktop images were upside down; not only that, when I tried to navigate anywhere on my upside-down desktop, the cursor mirrored my actions, travelling up when I was directing it down and left when I was directing it to go right. This mirrored-action occurred when using either the mouse or the touchpad.

Upside-down image and backward mouse? These have to be related, right?

I've had this laptop less then 2 months, it's an Inspiron 15, 5000 Series, Touch, and I am not finding Cortana's help at all helpful. 

Here is my question: I'd really like to know WHY the image went upside down and WHY the mouse/cursor began responding opposite to directional commands.  Is there an F-Key that my cat maybe stepped on to cause this to happen? (Otherwise I can only think that I have a ghost in the machine.)

My work-around was... I could not figure out how to get anything back to normal, and so I did what any novice would do: system restore. But this seems a little drastic, and I would like to know what could have went wrong, and so to perhaps learn a better way to fix this, in case it happens again.

Thanks, everyone, for any help or suggestions you have for me.  Please try to simplify your responses, recalling that I am very inexperienced, and getting on in years, and not too tech-savvy. I appreciate it.