Puzzles lovers everywhere are going to love the new puzzle app, Sevens by Nigel Hanbury. This Sudoku inspired game will hone your logic and problem solving skills and then push them to their limits. In Sudoku, you must place the numbers 1-9 in columns and rows such that the numbers only appear once in each row and column. Sevens takes this idea one step further. You must place the numbers 1-7 in rows and columns.