Detailed instructions for working a group puzzle of type 'Doug'
This is a signature puzzle named 'Doug'
The 4 elements in each group of this type of puzzle are: D, O, U, and G.
Every group in the puzzle must contain exactly this set of elements.
In a Doug puzzle, each row is a group numbered as shown in the figure above.
In a Doug puzzle, each column is a group numbered as shown in the figure above.
In a Doug puzzle, each 2x2 square is a group numbered as shown in the figure above.