/usr/include/crystalspace-2.0/csgeom/ is in libcrystalspace-dev 2.0+dfsg-1build1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/crystalspace-2.0/csgeom/aabbtree.h
/usr/include/crystalspace-2.0/csgeom/box.h
/usr/include/crystalspace-2.0/csgeom/bsptree.h
/usr/include/crystalspace-2.0/csgeom/chainhull2d.h
/usr/include/crystalspace-2.0/csgeom/csrect.h
/usr/include/crystalspace-2.0/csgeom/csrectrg.h
/usr/include/crystalspace-2.0/csgeom/dualquaternion.h
/usr/include/crystalspace-2.0/csgeom/fixed.h
/usr/include/crystalspace-2.0/csgeom/frustum.h
/usr/include/crystalspace-2.0/csgeom/kdtree.h
/usr/include/crystalspace-2.0/csgeom/kdtreex.h
/usr/include/crystalspace-2.0/csgeom/math.h
/usr/include/crystalspace-2.0/csgeom/math2d.h
/usr/include/crystalspace-2.0/csgeom/math3d.h
/usr/include/crystalspace-2.0/csgeom/math3d_d.h
/usr/include/crystalspace-2.0/csgeom/matrix2.h
/usr/include/crystalspace-2.0/csgeom/matrix3.h
/usr/include/crystalspace-2.0/csgeom/matrix4.h
/usr/include/crystalspace-2.0/csgeom/obb.h
/usr/include/crystalspace-2.0/csgeom/odesolver.h
/usr/include/crystalspace-2.0/csgeom/path.h
/usr/include/crystalspace-2.0/csgeom/plane2.h
/usr/include/crystalspace-2.0/csgeom/plane3.h
/usr/include/crystalspace-2.0/csgeom/poly2d.h
/usr/include/crystalspace-2.0/csgeom/poly3d.h
/usr/include/crystalspace-2.0/csgeom/polyclip.h
/usr/include/crystalspace-2.0/csgeom/polyidx.h
/usr/include/crystalspace-2.0/csgeom/polypool.h
/usr/include/crystalspace-2.0/csgeom/projections.h
/usr/include/crystalspace-2.0/csgeom/quaternion.h
/usr/include/crystalspace-2.0/csgeom/segment.h
/usr/include/crystalspace-2.0/csgeom/solidspace.h
/usr/include/crystalspace-2.0/csgeom/sphere.h
/usr/include/crystalspace-2.0/csgeom/spline.h
/usr/include/crystalspace-2.0/csgeom/subrec.h
/usr/include/crystalspace-2.0/csgeom/tcovbuf.h
/usr/include/crystalspace-2.0/csgeom/transfrm.h
/usr/include/crystalspace-2.0/csgeom/tri.h
/usr/include/crystalspace-2.0/csgeom/triangulate.h
/usr/include/crystalspace-2.0/csgeom/triangulate3d.h
/usr/include/crystalspace-2.0/csgeom/trimesh.h
/usr/include/crystalspace-2.0/csgeom/trimeshlod.h
/usr/include/crystalspace-2.0/csgeom/trimeshtools.h
/usr/include/crystalspace-2.0/csgeom/vector2.h
/usr/include/crystalspace-2.0/csgeom/vector3.h
/usr/include/crystalspace-2.0/csgeom/vector4.h