Today, my younger son came to me with a blue box made of metal. He looked happy.He open it and asked me, "Dad, you know it. Tell me how to play." I saw a lot of cards in the box and immediately understand what they were. The many different kinds of cool, paper cards were Duel masters, which had been popular among teenagers a few years ago.
It seems like that he found it in the closet of his older brother's room. The cards remained me of our old days, when my older son and I played them every day.
I have almost forgot the rule of Duel masters, so had to watch YouTube to remember it. What surprised me is that my younger son also watched the YouTube next to me, and understood the rule of Duel masters as good as what I understood.
Thereafter, as you guess, we spent hours playing the cards.