An Interactive Genetic Algorithm system is proposed for designing a car silhouette while involving the style designer in the evaluation process of a population of individuals. This IGA is based on the principle of an indirect encoding of a closed curve genome using a primary Fourier decomposition. A crossing over operator is proposed for mixing the parents' genes by a random weighted average into a new child's genome. A perceived similarity index between two genomes is built. It allows to check that our IGA is able to converge toward a targeted individual which was not present within the initial population and, consequently, that any silhouette in a style designer's mind could be revealed by our system.