Normal sudoku rules apply for the 9x9 grid. A cell outside the grid is a numbered room clue, to be determined by the solver. It indicates the digit which has to be placed in the Nth cell in the corresponding direction, where N is the digit placed in the first cell in that direction. Digits in a white circle must appear (at least once) as a sudoku digit or as a numbered room clue in the four cells around the circle. Digits in a black circle must NOT appear as a sudoku digit or as a numbered room clue in the four cells around the circle.