Time Out says
The reality of the online arena isn't just virtual in this anime saga of avatar conflict, which pays sly homage to---and often surpasses---spiritual predecessors such as Tron. Like that recently rebooted franchise, Mamoru Hosoda's film posits the pixelated and physical realms as parallel reflections of each other. (Appropriate to the film's duality fixation, IFC Center will be showing a dubbed version during matinees and a subtitled version in the evenings.)
While posing as the boyfriend of a young woman (Palencia) at her grandmother's 90th birthday, a lonely computer programmer (Sinterniklaas) cracks a mysterious numerical code that accidentally corrupts the globe's electronic infrastructure---and consequently, threatens nuclear doomsday. Modern reliance on technology is the story's nominal concern, though its unexpectedly multilayered vision of friendship, family and community is what gives this sci-fi film its soul. Here, the worlds of bodies and bits don't cancel each other out: Video-game slugfests are equated with flesh-and-blood baseball games, cyberwarfare meshes with ancient samurai combat, and social network affiliations are viewed as extensions of ancestral bonds. (Even the locales toggle between bucolic countryside and a gravity-free computer universe.) Summer Wars surprisingly celebrates togetherness and bravery as much as binary-mathematics expertise, all helped along by a kick-ass synthesis of traditional hand-drawn scenes and fluid, rainbow-explosive CG artistry.