Gradual change composition refers to the design technique in poster design where elements or colors transition smoothly from one to another, creating a visually appealing and dynamic effect. This approach is often used to draw attention to the main message or to guide the viewer's eye across the poster. A 'case' in this context would mean a specific example or instance of such a design. These designs typically showcase creativity in layout, color theory, and graphic elements, and can serve as inspiration for other designers.