How does this happen?

I have been blessed with a child who sleeps (on average) for 3-4 hours at a time. This makes night feedings tolerable.
I woke up today before 8, Kate wasn't up yet, so I decided to peek in on her.

This is her  typical sleep position (yup with her arms up above her head and everything):

This is what I saw:

There she was, squished in a ball in a completely different spot then I remember putting her in.
She will usually kick out of her blanket, or scoot a couple inches toward the center of the pack n play, but this is the first time she completely changed positions.

How does a 2 weeks old squirm so much that she moves across her bed?