Sandwich Sudoku is a great Sudoku variant that adds a bit of maths to the solving process. It follows the same rules as regular Sudoku in that each row, column and block must contain one of the numbers from "1" to "9". No number may appear more than once in any row, column, or block.
It differs in that it displays a number for each row and column. This number is the total of the cell contents that are between the "1" and the "9" for the corresponding row/column.

For example, in the puzzle to the right, in row 3 the sum of digits between the "1" and "9" must be 4. There is only one combination that gives 4 (ie the digit 4 itself) so the cell to the right of the "1" must be a "4" and the cyan colored cell must be a "9". Similarly, in row 5 the total must be 32. The only possibility for that is a combination of the digits "245678" ie 6 cells. So the "9" can only be in the cyan colored cell and the cell in column 1 has to be a "3".

All puzzles are solvable by pure logic alone - no guessing required. There is one new puzzle per day.
You may find these puzzles more challenging than regular Sudoku - remember you can use the "Solve a Cell" feature to help you along. Note that the puzzles do not require you to use regular advanced strategies such as naked pairs, box line pointing, x-wing etc. Make sure you watch the video walkthrough if this is your first time.