P has made and sold Pocky: a product line of thin, stick-shaped cookies. These cookies are partly coated with chocolate or a flavored cream; some have crushed almonds too. The end of each is left partly uncoated to serve as a handle. P makes Pocky in both a standard and an 'Ultra Slim' size. In 1978, P started selling Pocky in the United States. It also began registering U.S. trademarks and patents. It has two Pocky product configurations registered as trade dresses. P also has a utility patent for a 'Stick Shaped Snack and Method for Producing the Same.' The first thirteen claims in the patent describe methods for making a stick-shaped snack. The final claim covers '[a] stick-shaped snack made by the method of claim 1.' The width of that stick-shaped snack matches that of Pocky Ultra-Slim. In 1983, D started making Pepero. These snacks are also stick-shaped cookies partly coated in chocolate or flavored cream, and some have crushed almonds too. It looks like a Pocky. P sent letters to D asking it to cease and desist from selling Pepero in the United States. For the next two decades, P took no further action for more than three decades. In 2015, P sued D alleging trademark infringement and unfair competition, in violation of the Lanham (Trademark) Act §§ 32 and 43(a), 15 U.S.C. §§ 1114, 1125(a)(1)(A). The District Court granted summary judgment for D, holding that because Pocky's product configuration is functional, it is not protected as trade dress. P appealed.