How to start with Zen mojo application

I am not sure if I got the question right. If you already have a Zen or Zen Mojo application and would like to add a login page, I strongly recommend to develop the login page as a separate CSP/ZEN or Zen Mojo page. From my experience Zen Mojo is too heavy just to build a single simple login page (as it is designed for a complete SPA - single page application), so CSP or ZEN is recommended. If you are starting from scratch I usually recommend to pick a modern framework like Angular you feel comfortable with and communicate via JSON/REST to the backend. Responsiveness is usually achieved by a mix of picking UI libraries that are responsive by default (e.g. Bootstrap) and your own responsive CSS implementation. If you require a native application for mobile devices on iOS and Android (e.g. to interact with the camera) you have to be a bit more specific. But your options are either a native application (Swift or Java) or a hybrid (e.g. via Cordova or Ionic). The communication channel always is JSON/REST, so you have to start by designing your REST interface first, no matter what your web client looks like. At least for the majority of the use cases. Please let me know if you require additional information. HTH, Stefan