Sevens, from developer Nigel Hanbury, is a spin on the wildly popular Sudoku number puzzler, of which there are several variations in the App Store.
Just in case you've never played Sudoku before: The playing field consists of a 3 x 3 grid of squares. Each of the nine squares consists of yet another 3 x 3 grid.Your job is to fill in missing numbers from 1 to 9 in rows and columns without using the same number more than once in all the rows and columns. Depending on the difficulty of the level you're attempting to play, some numbers already will be filled in to help you get started. It's not like arithmetic; it's more a process of elimination or fill-in-the-blanks.