Normal sudoku rules apply. The grid is covered mostly in darkness. Placing correct digits in cells will illuminate more of the grid. Cells are either wall or cave cells. Walls are orthogonally connected to the edge of the grid and the cave is one orthogonally connected area. A 2x2 area cannot be fully wall nor fully cave. White circles are cave cells and the value in a circle is the number of cave cells “seen” in that row and column, including the cell itself. Walls obstruct vision. A cage contains no repeated digits, and the values of the cave cells sum to the given total. Wall cells don’t count towards the sum. (Note: A cage’s clue doesn't necessarily appear in the uppermost nor leftmost cell.) A doubler appears exactly once in each row, column, and 3x3 box. For purposes of circles and cage sums, such cells’ digits are doubled in value. Each digit is doubled once.