Here is an overview of the device, via Nintendo:
Game & Watch: Super Mario Bros. features a modern +Control Pad. In addition to playing classic games Super Mario Bros., Super Mario Bros.: The Lost Levels (released in Japan as Super Mario Bros. 2), and a special version of Ball with a Mario makeover, Game & Watch: Super Mario Bros. also functions as a clock, with 35 little touches to discover, including some guest appearances from Mario’s friends and foes.
Watch a trailer below. View a set of images at the gallery.