Snapchat’s developer platform is blowing up as a gateway to teen social app users. Hoop is the latest Snap Kit blockbuster, rocketing to #2 on the overall App Store charts this month with its Tinder -esque swiping interface for discovering people and asking to message with them over Snapchat. Within a week of going viral, unfunded French startup Dazz saw Hoop score 2.5 million downloads.