The Secret World of Arrietty, about a teeny-size 14-year-old girl who lives with her family beneath the ­floorboards of a big house and the human-size boy who befriends her, is adapted from British author Mary Norton's wonderful ­children's fantasy novels, The Borrowers. The lyrical animation, with its meditative attention to nature, bears the unique stamp of Japan's Studio Ghibli, cofounded by the great ­Spirited Away animator Hayao Miyazaki. The result is a dreamy, soft-edged hybrid, equally interested in observing ­raindrops and the worries of a race of ­minuscule beings. B+