The sun brings light to the city, but there are always dark spaces in the city that cannot be reached by the sun, so we explore the possibility of introducing natural light into the dark space and interacting with it. The dark staircases of old residential buildings in the old city have no substantial effect but become places for dirt and dust. At the same time, there are not enough places for children to play in the old city. We use a device that is installed on the wall which would otherwise block the light. Turn it into a prelude of light. This device not only introduces light, but also defines the entire space. The original dark and negative were replaced with bright and lively. Moreover, the device protrudes from the wall, changing the sharp and cold character of the original space. The device we designed starts from cost and feasibility. A very simple unit structure is designed. The glass ball rotates uniaxially, and the mechanical transmission device rotates the filter glass to change the color of the incident light. Use this to control the overall effect. Taking into account the low income of the region, and the quantity demand for use. The simple mechanical structure can not only control the manufacturing cost, but also greatly reduce the maintenance cost in the later stage. It is also easy for children to adapt and explore more possibilities. The natural light "made" into children’s natural toys, turning the original dark stairs into a joyful paradise for children.