   // Set the color of the background
   glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
   glDisable(GL_DEPTH_TEST);
+
+  // Set perspective mode
   glViewport(0, 0, window_width, window_height);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();

  fprintf(stdout, "   simtime:%f\n", sim_time);
}

__host__ void Keyboard(int key, int x, int y) {
  if (key == GLUT_KEY_RIGHT) {
    rY += 15;

   positions[y * width + x] = make_float4(u, w, v, 1.0f);
}

// Function called when incorrect command line syntax is called or -h flag is passed
__host__ void help() {
   fprintf(stderr,"./boids --help|-h --nboids|-n \n");
}

// Function to setup and launch kernel
__host__ void launchKernel(float4* positions, unsigned int width, unsigned int height, float t) {
  dim3 dimBlock(16, 16, 1);
  dim3 dimGrid(width / dimBlock.x, height / dimBlock.y, 1);
