idris-box2d

You need to be able to link with -lBox2D and use #include <Box2D/Box2D.h>. This most likely necessitates installing Box2D through your distro's repositories, otherwise you might manually need to dabble w/ the include/linkage options throughout this project (Idris directives in Physics/Box2D.idr and stuff in the Makefile). steshaw/idris-sdl2 has an example of how to do it properly when pkg-conf files are available.