What looks like one big block is actually 4 blocks.
The ones that look like they are on top of each other are actually 3 blocks of one color and the 4th block is a different color or a block turned a different direction.
Take a couple of pieces of paper and make 8 blocks 4 each of two colors. Just make them small and color them. rearrange them and you will see what I mean.
Here's a similar one I made.
[IMG]
http://i166.photobucket.com/albums/u...etheblock2.jpg[/IMG]
HTH
:D