Since Version XE2, RAD Studio has included FireMonkey. FireMonkey is an amazing library. It is a really ambitious target for Embarcadero, but it's important due to its mid and long-term strategy. VCL is and will remain a Windows-only library, while FireMonkey has been designed to be completely OS and device independent. You can develop one application and compile it anywhere (if anywhere is in Windows, OS X, Android, and iOS; let's say that it's a good part of anywhere).
One of the main features of FireMonkey is customization through styles. A styled component doesn't know how it will be rendered on the screen, because the style is in charge of it. By changing the style, you can change any aspect of the component without changing its code. The relation between the component code and style...