In an empirical case study of software tools, two participants used the ITS style designer's language to implement a general purpose, executable, rule-based user interface style. This language allows style designers to select, combine and modify rule prototypes in order to construct a rule-based user interface style. The participants implemented the entire IBM CUA-2 user interface style, plus nine additional human-computer interaction techniques, in 5–7 person-weeks. This is impressive productivity. Typically the time to complete a single CUA-2 application is measured in person-years, not person-weeks. The style implemented here is reusable by any ITS-implemented application. The achievement reported here shows that about half the work of all ITS-implemented CUA-2 applications has been completed in a few person-weeks. This result demonstrates the power and productivity of the ITS approach and tools. The results of this case study showed that key ‘ready-mades’ (e.g. named attribute groups) provided in the style designer's toolkit could be used intact, which is important for importing or exporting interaction techniques from one style to another style. The results generalize to other computer-literate designers who may want to use these tools to create other user interface styles.