My Favorite Smartphone App

My favorite smartphone App is "Yu-Gi-Oh DUEL LINKS".
This is the social game application. "Yu-Gi-Oh DUEL LINKS" is based on a card game and a comic.
I loved this a card game and a comic when I was elementary school student. So, when I play this game, I always feel nostalgia.
In addittion, some friends of mine play this game too, and we talk about and play with this app. This is one of the reason I like it.