This study bridges the theory-practice divide in learning design by adapting the Learning Design Triangle (LDT) framework to guide co-design processes. Conducted in Mainland China, it follows an experienced teacher redesigning a first-year engineering course. Findings highlight a transition toward skill-oriented outcomes, active learning strategies, and improved alignment between pedagogy and assessment. It offers practical guidance for facilitating teachers' transition to student-centered learning design, providing both tools and insights for systematic course improvement.