Horror games represents a very specific genre specifically designed to elicit fear. These games provide a tremendous emotional experience balanced between stress and satisfaction. Yet, over time, the player acquires further insight of the mechanisms of the game, dissipating the creepy climate that reduces the emotional impact intended. This paper hypothesises that exploring existing facets within a game such as visuals and sounds might establish a good approach to renew the gaming experience. To understand the players emotional reactions towards context alteration an adaptation of a published game (P.T. by Konami 2014) was used. This context refers mainly to light effects, sounds and in-game events. To learn which game effects induce the strongest physiological reactions, an experiment was conducted and correlation between the physiological data, collected through the measure of the galvanic skin response (GSR), and that of the perceived emotion provided by participants, was investigated. Results show that the order in which effects are arranged can produce extensive emotional responses. They also suggest that psychological impact can be increased not only by the visual horror itself, but also through the process that slowly builds up to it, in particular the usage of sounds.