When I was visiting family for the holidays, my father was solving the "Paint By Sudoku" book that was out in the States, which is just a bunch of Paint By Number/Hanjie puzzles and has nothing to do with sudoku. I thought I should finally construct some puzzles that are truly paint-by-sudoku (I had made an earlier attempt, but this is much better).

This variation uses the standard style of a japanese sum puzzle in its outer constraints. The outside numbers refer to the sums of consecutive touching digits (or a single digit) as they appear in order in the puzzle by row/column with at least one space present between any region. If an outside constraint is, say, 15, then there must be a set of numbers (12345, or 69, or many other choices) that sum up to 15 in that row/column. If an outside constraint is 15 and then 9, then there must be a set of numbers that sum to 15, then at least one "space", and then a set of number(s) that sums to 9.

In this painting variation, you are actually meant to shade in the regions that are indicated by the outside numbers and at the end of the puzzle you will have both a valid sudoku and a fitting picture. People who like Killer Sudoku or Kakuro will appreciate how sums must be used in these puzzles to proceed.

I've written up a little more on my blog as well as made a new Hanjie variation here (with solutions), but the three paint-by-sudoku puzzles I'm sharing with indicated difficulties are below.