Sandwich Sudoku comes from Nick Carney. This game was popularized in the spring by Alex Bellos via his puzzle column in The Guardian. 

It's a standard sudoku with one significant difference: the numbers above the grid, and to the side of the grid, are the sums of the numbers that separate the 1 and the 9 in that column or row.

Puzzlers who have played Killer Sudoku (see link below) and Kakuro should be able to jump right in.

The game has only 40 levels, but that's okay! These games have been taking me a long time to solve.  At the moment I've solved 13 levels totaling about 6 hours of fun.  By that measure, $5 is cheap.

This game is fantastic.

My Solving Times
Level   Time
1          14:07
2          31:04 3          26:32
4          26:05
5          11:40
6          44:40
7          23:07
10        26:50
11        31:23
13        28:44
14        23:36
16        21:50
17        24:22

https://apps.apple.com/us/app/sandwich-sudoku/id1476116705

Other Innovative Sudoku Puzzle AppsKropk'i Sudoku  This is really a Latin Square with a couple of innovative ideas. It plays fast.Quindoku Same as Logi5PuzzLogi5Puzz  Same as NumDom. Bu...