This design-based research study was conducted to identify what importance of a tangible user interface (TUI) can add to teaching and learning. Over a 2-year period, teachers ("n"?=?39) and students ("n"?=?145) participated in the study. The identified problem for investigation was how students, including those with low fine motor skills and those with learning difficulties, develop geometry concepts combining cognitive and physical activity. A didactical application was designed during the first iteration and implemented in inclusive classrooms during the second and third iterations. Qualitative research methods were applied. A relationship between diverse students' needs and geometry concept learning in relation to computer-supported learning by TUI was discovered. Two dimensions were identified: (1) TUIs support concept development, with physical and virtual representations based on dynamic geometry assisted by TUI; (2) TUI manipulative properties support students who have low motor skills and difficulties in their geometry learning as well as in their inclusion in classroom activities. The study outcomes contributed to the design process of the TUI didactical application and its implementation in inclusive classrooms, and to the body of knowledge in teaching and learning geometry concepts applied for computer-assisted learning environments supported by TUI.