It's not easy but it's very fun.
The Solitaire Zero21 Madness card game is a different approach to the classic solitaire games, this game will trains your brain with super solitaire experience. It is an offline game which you can play solitaire on anytime and anywhere.
Level duration is 30 seconds so you must think fast or use a superpowers. There are 2 modes of the game one normal and insane mode where cards are shuffled every 5 seconds. It's not easy but it's very fun.