[logicalmonster]

Is there any particular reason based on this system to go 1-2-3 vertically instead of horizontally? I was a bit confused until I noticed the box numbers in the upper-right corners. In many languages, we read left-to-right, so I expected to see the the next block to the right of the first one.

[thomasteepe]

For me, it's a natural consequence of filling a box line-wise vertically from top to bottom. If you want to use the sheet layout variant with 3 columns and boxes of variable height rather than a fixed 3x3 layout, the vertical scheme seems again more natural.

But whoever feels more comfortable with a horizontal scheme should do so.