Ahhh. So you used a wrapper or a library? Interesting then. I had assumed that almost every rendering method enables frustrum, occlusion, and backface culling by default if only to clear the number of objects needed to be tracked in memory. One thing I noticed in your game is that it's based on the absolute mouse position, which with a 16:9 window makes it difficult to turn in certain situations because your horizontal movement space is much larger than the vertical movement space and that adversely affects turning speed. Changing so that is based just on horizontal mouse movement or adding keyboard controls might be better.

If I remember my graphics accelerator history correctly per-vertex lighting using Gouraud shading was the method SGI made standard with OpenGL in 1992, before 3DFX and ATI came in and made per-pixel via Blinn-Phong just as computationally efficient in about 2000 or 2001. Used before Gouraud and then alongside per-vertex and per-pixel was per-face flat shading, which kept being used up until the Xbox 360/PlayStation 3/DirectX 10 era. Face normals for per-pixel started being used in 1999 by SEGA, but stopped being common around the same time as normals flat shading got abandoned.

If I'm wrong please feel free to correct any of this, it's been about eight years since I last learned all of the different methods.

Thanks for clarifying, so I guess I already have it on then.