Doing my head in now!

Can someone explain how this works?

How can a piece of chocolate that has 5 rows and 5 columns, get broken up and then put back together again - back to 5 rows and 5 columns but have a small piece left over?

please log in to view this image

I cant work it out how its doing it!

 

Keep your eye on the big chunk that slides across. It changes size.

 

No it dont

 

it looks like it does to me

 

This keeps hurting my eyes staring at it for periods of time

 

No, it slides up but remains the same size!

 

Where did you get it from?

 

Here we go it does get bigger
http://www.mirror.co.uk/news/weird-news/watch-disappearing-chocolate-bar-magic-3722941

 

I can't unsee this now and it is getting annoying... HOW IS IT DOING THAT!

 

It had to come from the flipping mirror paper didnt it

Here is a clip showing it...

 

Mate, this will sound sad but I have seen this more times than we had fans at the parade yesterday and if it wasnt for seamge giving the answer away after cheating looking it up, I would still be struggling now! I even got a little ruler measured it on the screen and everything. Me next step was to actually buy a chocolate bar and try it myself. But I didnt have enough change on my to buy a big bar at the corner shop and I wasnt prepared to pay £1 charge for using my card. Rip off shop.

Now seamge has cheated and given it away, I have been on youtube to get clearer explaination and above is what I found.