I'm not much into pop and not much into Katy Perry. I concede that she's OK to look at and her song productions are entertaining. I also concede that I'm just a nubie when it comes to music theory and song writing. Still all in all, this article was fun for me... "Explaining the genius of Katy Perry’s “Teenage Dream”—using music theory"
http://www.slate.com/articles/arts/culturebox/2014/03/katy_perry_s_teenage_dream_explaining_the_hit_using_music_theory.html .
"It takes a lot of devotion and work, or maybe I should say play, because if you love it, that's what it amounts to. I haven't found any shortcuts, and I've been looking for a long time."
-- Chet Atkins