The design of the lighting environment is important for determining room specifications. Recently, systems that can change the lighting environment in a room by controlling the direction and intensity of light using a computer have been proposed. However, with such a method of controlling the light, it is easy to specify the size and position of the brightly illuminated area, but not the darkened area. In this study, we controlled shadows and proposed a method for controlling dark areas. We construct Spot Shadow, a system that can generate shadows of arbitrary sizes and shapes at positions specified by users. The prototypes of a tabletop system and a large system can create shadow generation areas of 1m × 0.9m and 7m × 4.3m, respectively. This study proposes a method for manipulating shadows and demonstrates new possibilities for creating interactive spaces using shadows.