Normal sudoku rules mostly apply; however the grid contains no 5s. Instead every row, column and box has a single repeated digit. (NB Beware! This does NOT mean that you could find nine cells in which 5s could be placed to make a genuine grid!) Additionally: divide the grid into rectangular regions of orthogonally connected cells. Each rectangle contains exactly one circle. A single cell with a circle counts as a 1x1 rectangle. A number in a circle represents how many cells are in the rectangle the circle belongs to. Rectangles cannot overlap. Every cell in the grid is part of a rectangle. Digits may not repeat in a rectangle.