So far, we have learned that FMX has the capability to apply different styles to the same application. A style is composed of a list of definitions (one for each UI element, that is, component) that are built as a composition of basic elements (like shapes or images) and/or other styled elements, making the whole mechanism really powerful and extensible.
If you are an experienced VCL developer, you can see the style definition as a sort of DFM file, where the structure of components is defined together with property values determining specific characteristics of each element. We never addressed the fact it is not trivial to provide a complete definition of the visual asset of a component.
This becomes even harder while keeping in consideration that this definition should be sophisticated enough to deliver a proper version of the component for each supported platform (up to five different platforms!) and considering all the surrounding difficulties...