Tinder. It was Tinder. But Mark said that he was leaving in eight months for residency and Colin was looking for real commitment, so that was the end of that. But when Colin saw on another app that they were a 96% match, he gave it another shot--and even changed some of his answers to match Mark's. Of course, Mark (details oriented as always) noticed the percentage increase from 96% to 98% as they were chatting, and this would be the first time he would experience Colin's...enthusiasm. Shortly thereafter, they met up for gyros at Greek Lady, and the rest is history.