Katy Perry’s life is all cotton-candy kisses, fireworks on the beach, and drunken Friday nights. And throughout her second album, she sings about the fun she’s having living it up with her BFFs. (Market crisis? Oil spills? What war?) Teenage Dream is pure escapism, and the perky Perry sells it hard here. Whether thinking about an old crush or quoting Madonna, she’s a glowing orb of energy, soaking in the hook-filled rays of the album’s prefab pop. “California Gurls” is summer’s frothiest jam and one of Teenage Dream’s sturdiest anchors; the title cut and “Hummingbird Heartbeat” are also top-down bangers. Perry is best when she’s riding rainbow-colored unicorns in the land of bowling-ball-sized marshmallows — the tough girl she plays in the slightly sinister “Circle the Drain” and the gothic whining of “Who Am I Living For” sound forced. Teenage Dream sags a little in its second half, but think of it as the last days of a sweltering summer creeping into a slightly cooler fall.