// For portability, include these lines at the beginning of each of your files. 

// windows.h needed for Windows 2000/Visual Studio 
#ifdef WIN32
  #include <windows.h>
#endif

// MacOS uses frameworks/different paths 
#ifdef __APPLE__
  #include <OPENGL/gl.h>
  #include <GLUT/glut.h>
#else
  #include <GL/gl.h>
  #include <GL/glut.h>
#endif