By using grids and all the styles we saw in the previous section, in many cases you won't need anything extra in order to build a responsive website. However, in some cases moving components around, resizing them, or even hiding part or all of them, isn't enough. For example, you may actually want to show totally different components for small and large screens—say, a screen with three tabs for a phone, showing only one tab at a time, but a three-column display for a desktop, showing everything simultaneously. Changes could be even more drastic: you might decide that some functionality isn't going to be available on mobile devices, but only included in large screens. So, instead of doing responsive design, you are delving into adaptive design, meaning that the actual design and functions of the screen will change, and then we need to be able to handle internal changes in code.