Normal sudoku rules apply. Some cells in the grid contain a given digit, and these have all been circled. A circled given digit indicates how many times that digit appears as a circled given digit in the grid. Unfortunately, most of these given digits are obscured by fog. Entering a correct digit will clear the fog in that cell, and maybe other cells too. No guessing is necessary. A black dot sits between two digits where one is double the other. The two digit number to be discovered in the blue frame (reading left to right) will indicate the total number of circled given digits that exist in the grid.