"We all move forwards dear."
"Yes, granny" Sighed Jake. Granny had her explaining voice on again.
"There are those rare ones who can move side-to-side. And then there are the rarest of the rare ones. The special ones..." Jake pricked his ears.
"What special ones granny?"
"They are so rare! One in a billion. There are likely only six or seven in the world out of everyone!"
"So why are they rare granny?"
"Oh ho! They can do something that no-one else can do. They can move backwards!"
"I don't understand granny."
"That's alright boy. You will..."