In the abandoned ruins, the protagonist who can emit light by itself and a shadow existing in the wall meet. Then, through cooperation in solving puzzles, they overcome various small obstacles and receive certain rewards. The light source of the protagonist projects light and combines with the obstacles to project shadow platforms on the wall for the shadow to pass through. The shadow presses the buttons and mechanisms on the wall to open the obstacles (doors/other obstacles) in front of the protagonist on the plane, and the two cooperate to complete the game and finally achieve each other's salvation: they coexist and thrive together.