Normal sudoku rules apply. Every row, column and 3x3 box contains exactly one "doubler" cell. A digit in a doubler cell counts for twice its value for the purposes of all cage sums. Digits in doubler cells form a unique set of the digits 1 to 9. Digits may not repeat in cages, though values might. (eg a cage may not contain a doubled 2 and a regular 2 but may contain a doubled 2 and a regular 4). Caged cells must sum to the value indicated in the top left corner of the cage. The cell with a grey circle contains an odd digit. The cell with the grey square contains an even digit.