Playful hedonism may be Katy Perry’s hallmark (“Yeah we danced on tabletops and we took too many shots/Think we kissed, but I forgot”, she burbles on “Last Friday Night (T.G.I.F.)”, but there’s a palpable, laser-sighted focus to this second album. Once more masterminded by banger architects Dr. Luke, Max Martin and Benny Blanco, it leaps giddily from euphoric dance uplift (“Firework”) to glitchy electronica (“E.T.”). Polished, challenging and precise, this is bubblegum with a bite.