While the core engine is written in C++ with SDL2, there is an easy to use modding interface, by using it, it’s possible to create entirely new games. On the Flare website's Mods page, you can find games made by the Flare team, as well a few select community projects.
This package only provides the Flare engine, gameplay mods can be installed through other packages or by putting them manually in 'non-packaged/data/flare/mods'.