Flexibility and efficiency are key criteria for the quality of interactive systems. Flexibility means accommodating diverse user needs, skill levels, and usage contexts—through customizable interfaces or alternative interaction methods. Efficiency refers to how quickly and easily users can achieve their goals, especially in repetitive tasks. Both aspects contribute to user satisfaction and productivity. A balanced combination of flexibility and efficiency enables both novices and experienced users to interact effectively and comfortably, enhancing usability and overall system performance.