Psychophysiological measurements have so far been used to express player experience quantitatively in game genres such as shooter games and race games. However, these methods have not yet been applied to casual video games. From a development point of view, games developed in the casual sector of the games industry are characterized by very short production cycles which make them ill-suited for complex and lengthy psychophysiological testing regimes. This paper discusses some methodological innovations that lead to the application of psychophysiological measurements to enhance the design of a commercially released casual game for the Apple iPad, called 'Gua-Le-Ni'; or, The Horrendous Parade'. The game was tested in different stages of its development to dry-run a cycle of design improvements derived from psychophysiological data. The tests looked at the correlation between 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, and the enjoyment the designers had in mind for this product. In this paper, we discuss the changes that were made to the game and the data-analysis that led to these changes.