If you look at it just right, you'll see how the title of the puzzle arises from how the regions appear as blocks built upon and supporting each other.
The official rules:
- The digits 1 through 9 appear in each row and each column exactly once.
- Digits in each shaded region must multiply to the indicated product.
- Squares with multiple colors contain a number that’s used in the product for adjacent regions of each of those colors.
- Remember: numbers can repeat within a shaded region if that doesn't violate the first rule.