What is Hyper Sudoku?

Hyper Sudoku is also named Windoku because of the similarity with a window with glazing bars. The layout is identical to a classic Sudoku, but with additional interior areas defined in which the numbers 1 to 9 must appear. These four new areas are overlapping with the nine standard regions of a Sudoku.

The solution approach is similar yet different to the solution approach of a Sudoku. The difference is that the 13 regions are more major in the solution process.