Normal sudoku rules apply. Each cage is either full of "oil" (even digits), full of "water" (odd digits), or a mix of both. In all cases, each "row" within a cage is of just one type (oil or water). Oil floats on water, so even digits will always be in rows above odd digits in mixed cages. Digits in cages do not repeat and must sum to the small clue, if given. Black dots separate two digits where one is double the other.