Openbravo's modular architecture makes simple development of extension modules possible. Modularity allows people to develop extensions and to distribute them independently, as well as to leverage distribution channels. The number of available commercial and non-commercial modules is growing and dissemination of modules is growing alongside. To avoid inconsistency or substandard user experiences, guidance must be given to the community on how to create high quality, usable, enjoyable and consistent modules and customized Openbravo windows. We have created two documents to help you in doing so. The starting point is the User Interface Guidelines wiki document that describes the main rules and tips for Openbravo 3 module and window design. In addition to this, we have built a mockup tool that lets you design Openbravo windows without coding. It is simply a shared presentation document that has templates and library components that lets you design your own windows and flows. Make sure to read the instructions before using it.