Description: Categorize the fantastic paper-animals before they flee the bestiary which contains them! Use the taxonomic cubes! Feed the brutes! Double Jungle's 'Gua-Le-Ni, or: The Horrendous Parade' is the first commercially-released casual video game whose development and tuning were guided by the analysis of its players' psychophysiological responses. Starting from very early builds, The Academy for Digital Entertainment at NHTV Breda University of Applied Science (The Netherlands) assisted the Italian development team of Double Jungle in obtaining a detailed insight into the psychophysiological (or biometric) effects that their casual action-puzzle videogame had on its target audience. In particular, our experiments correlated stress levels and the contraction of facial muscles with in-game performance in order to establish whether 'Gua-Le-Ni' offered the cognitive challenge, the learning curve, the duration and the enjoyment the designers had in mind for their product. Taxonomy has never been so much fun!