Kirigami
Introduction
Kirigami is KDE’s powerful but lightweight user interface framework for mobile and convergent applications. It allows Qt developers to easily create applications that run on most major mobile and desktop platforms without modification (though adapted user interfaces for different form-factors are supported and recommended for optimal user experience). It extends the touch-friendly Qt Quick Controls 2 with larger application building blocks, following the design philosophy laid out in the KDE Human Interface Guidelines.
You can try out Kirigami in action with the Kirigami Gallery app which is available on most Linux distributions. On Android, you can download it from Google Play Store. The source code of kirigami-gallery can be found at this Git repository.
Kirigami uses CMake as its build system of choice. If you're unfamiliar with CMake, the CMake Manual for Qt is a good starting point to learn more about it.
Get It!
Kirigami is part of KDE Frameworks and is released together with other frameworks every month. In most cases, you'll want to use your Linux distribution's packages. You can also find source tarballs for the latest stable releases from download.kde.org. If you want to get the latest version of the source code, you can clone Kirigami from this Git repository. Check out the KDE Community Wiki for a handy guide to building software from source.