Normal sudoku rules apply. The black dot joins digits in a 1:2 ratio (ie one digit is double the other). Not all dots are given. The sum of the digits along a grey line is equal to the sum of the digits in the circles at either end of the line. Shade some cells such that all shaded cells are orthogonally connected and all unshaded cells are orthogonally connected. No 2x2 area may be fully shaded or fully unshaded. The circles act as 'minesweeper' clues. Ie Cells containing a circle are always unshaded, and their value is the number of shaded cells in the surrounding 3x3 area (i.e. the up to eight cells that touch the circle either orthogonally or diagonally).