Set during another languorous Brooklyn summer, Hittman’s debut follows 14-year-old Lila (a fearless Gina Piersanti), awkwardly and constantly exposed to the sexual exploits of her older friend Chiara (Giovanna Salimeni), who goes through boyfriends and experiences with the kind of ease that Lila can scarcely imagine. While “Beach Rats” isn’t an official sequel to Hittman’s previous film, “It Felt Like Love,” the filmmaker explores similar themes and structures and both, told from seemingly opposite vantage points.