Retro Number is a free and simple application for Apple Watch and iPhone. It contains four kinds of games that train your brain. Let’s try and improve your intellectual ability. -Couple Tap the same numbers as fast as you can. -Flash Memorize the randomly placed numbers in 5 seconds. -Reflex Just tap the numbers from 1 to 9 in order as fast as you can. -Line Swap and align the same three numbers vertically, horizontally or diagonally.