Either you want to train your brain or just kill time, the game of Sudoku fits its purpose.
I’ve been doing a lot of Sudoku a couple of years ago and at the moment I need to train my brain, sharpen my senses. Therefore I recomand the SUDOKU apps. On GOOGLE PLAY (ANDROID) when you seek for apps, you can see some that are recommended: it reads ‘EDITORS’ CHOICE’. My belief is that it’s wise to AT LEAST give those kind of apps a shot.
I’ve installed the top app. It should be available on APP STORE(iOS) as well. If not THAT particular one, then others. After all, the mechanics of SUDOKU is the same, no mather the developer or title.