The purpose of this master's thesis is the display, explanation and description of the process of development and the implementation of the elements of the atmospheric psychological horror game Kuroi Yuki. All of the elements used in the development of this videogame are shown and all of the scripts and components connected to the functionality and design are explained. Furthermore, the way that the themes and the atmosphere/ ambiance in a videogame of this genre are amplified is explained and the optimal way to implement such a concept is concluded. In Kuroi Yuki, there exist unique elements such as the Mind's Eye ability to peer into an alternative dimension and the rarely seen way of attacking seen in the Smoldering Gazer enemy, which includes dragging the players camera towards the Gazer's Eye. The way in which the Black Snow is made is explained along with the particle system, post processing, animation, UI elements, scripts with which we control the elements in the game, player movement and many more concepts within Kuroi Yuki. The readers of this thesis will ultimately learn many different approaches and concepts about the development of three-dimensional first-person videogames and will greatly further their knowledge of making atmospheric psychological horror videogames.