The PAL Engine is a custom game engine meant to run on Palygon, a hexagonal tamagotchi type device. Development and more info on the physical device can be found here.
The PAL Engine is platform agnostic and is comprised of game logic, an entity system, graphics and sound library, and a physics engine. To build a project with the engine, a backend file has to be created for the PAL (Palygon abstraction layer) to operate properly and interact with hardware. In the example directory, this file is called pal_backend.c, but no naming convention is enforced. The example directory's CMakeLists.txt has more information about variables to set for building to work.