In its lifetime, the Wii U has sold just under 4 million units worldwide. The 3DS sold nearly that amount in the first half of Nintendo's current fiscal year alone. If this is your first episode, Friends List is a daily web series in which members of Polygon's editorial staff answer an important, unusual or agitating question related to video games. The goal is to give Polygon's many team members across the globe an opportunity to speak with you directly via video. Today, Deputy News Editor Griffin McElroy and Reporter Dave Tach answer this question: Why is the 3DS thriving while the Wii U flops?