back_buffer, back_lpitch); // video buffer and memory pitch

   Draw_Pixel16(path[index].x, path[index].y, RGB16Bit(255,255,255), back_buffer, back_lpitch);
   Draw_Pixel16(path[index].x+1, path[index].y, RGB16Bit(255,255,255), back_buffer, back_lpitch);
   Draw_Pixel16(path[index].x, path[index].y+1, RGB16Bit(255,255,255), back_buffer, back_lpitch);
   Draw_Pixel16(path[index].x+1, path[index].y+1, RGB16Bit(255,255,255), back_buffer, back_lpitch);

    } // end for index

// lock back surface
DDraw_Unlock_Back_Surface();

} // end Draw_Waypoints

// T3D GAME PROGRAMMING CONSOLE FUNCTIONS ////////////////

int Game_Init(void *parms)
{
// this function is where you do all the initialization 
// for your game

int index; // looping variable

// initialize directdraw, very important that in the call
// to setcooperativelevel that the flag DDSCL_MULTITHREADED is used
// which increases the response of directX graphics to
// take the global critical section more frequently
DDraw_Init(WINDOW_WIDTH, WINDOW_HEIGHT, WINDOW_BPP, WINDOWED_APP);

// load background image
Load_Bitmap_File(&bitmap16bit, "RACETRACK24.BMP");
Create_Bitmap(&background_bmp,0,0,640,480,16);
Load_Image_Bitmap16(&background_bmp, &bitmap16bit,0,0,BITMAP_EXTRACT_MODE_ABS);
Unload_Bitmap_File(&bitmap16bit);

// load the car bitmaps
Load_Bitmap_File(&bitmap16bit, "SIMIMG24.BMP");

// create car bob
Create_BOB(&car,334,64, 16,16, 16, BOB_ATTR_MULTI_FRAME | BOB_ATTR_VISIBLE, DDSCAPS_SYSTEMMEMORY,0,16);

// set floating position and direction to west
car.varsF[0] = car.x;
car.varsF[1] = car.y;
car.curr_frame = 12;

// load the car in 
for (index=0; index < 16; index++)
    Load_Frame_BOB16(&car, &bitmap16bit, index, index, 3, BITMAP_EXTRACT_MODE_CELL);

// unload car
Unload_Bitmap_File(&bitmap16bit);

// initialize directinput
DInput_Init();

// acquire the keyboard only
DInput_Init_Keyboard();

// initilize DirectSound
DSound_Init();

// load background sounds
wind_sound_id = DSound_Load_WAV("WIND.WAV");
car_sound_id = DSound_Load_WAV("CARIDLE.WAV");

// start the sounds
DSound_Play(wind_sound_id, DSBPLAY_LOOPING);
DSound_Play(car_sound_id, DSBPLAY_LOOPING);

// hide the mouse
if (!WINDOWED_APP)
   ShowCursor(FALSE);


// return success
return(1);

} // end Game_Init

///////////////////////////////////////////////////////////

int Game_Shutdown(void *parms)
{
// this function is where you shutdown your game and
// release all resources that you allocated

// shut everything down

// kill all the bobs
Destroy_BOB(&car);

// shutdown directdraw last
DDraw_Shutdown();

// now directsound
DSound_Stop_All_Sounds();
DSound_Shutdown();

// shut down directinput
DInput_Shutdown();

// return success
return(1);
} // end Game_Shutdown

/////////////////////////////////////////////////////////////////

int Game_Main(void *parms)
{
// this is the workhorse of your game it will be called
// continuously in real-time this is like main() in C
// all the calls for you game go here!

int index; // looping var

static float speed = 0; // speed of car

static int curr_waypoint = -1,
           test_waypoint;

static int display_debounce = 0; // used to debounce keyboard

int ai_on = 1; // used to enable display ai based on user taking controls

// start the timing clock
Start_Clock();

// clear the drawing surface
DDraw_Fill_Surface(lpddsback, 0);

// lock back buffer and copy background into it
DDraw_Lock_Back_Surface();

// draw background
Draw_Bitmap16(&background_bmp, back_buffer, back_lpitch,0);

// unlock back surface
DDraw_Unlock_Back_Surface();

// draw the waypoints
if (vector_display_on==1)
   Draw_Waypoints();

// read keyboard
DInput_Read_Keyboard();

// is user toggling vector display
if (keyboard_state[DIK_D] && !display_debounce)
   {
   display_debounce = 1;
   vector_display_on=-vector_display_on;   
   }  // end if

if (!keyboard_state[DIK_D])
    display_debounce = 0;

// these controls not really needed since AI drives...

// allow player to move
if (keyboard_state[DIK_RIGHT])
   {
   if (++car.curr_frame > 15)
      car.curr_frame = 0;

   // turn off ai this cycle
   ai_on = 0;
   } // end if
else
if (keyboard_state[DIK_LEFT])
   {
   if (--car.curr_frame < 0)
      car.curr_frame = 15;

   // turn off ai this cycle
   ai_on = 0;
   } // end if

if (keyboard_state[DIK_UP])
   {
   if ((speed+=0.1) > 4)
      speed = 4.0;

   // turn off ai this cycle
   ai_on = 0;
   } // end if
else
if (keyboard_state[DIK_DOWN])
   {
   speed-=0.1;

   // turn off ai this cycle
   ai_on = 0;
   } // end if

// ai speed control -- pretty dumb huh :)
// better to tie it to angle that it's turning
if (ai_on)
   if ((speed+=0.05) > 4)
      speed = 4.0;

// apply friction
if ((speed-=0.01) < 0)
      speed = 0;

// make engine sound
DSound_Set_Freq(car_sound_id,11000+speed*2000);

// let ai turn the car

// find nearest waypoint first
test_waypoint = (Find_Nearest_Waypoint(car.varsF[0],car.varsF[1])+1)%NUM_WAYPOINTS;

// test if this is a new waypoint and not the last
if (test_waypoint != curr_waypoint)
   curr_waypoint = test_waypoint;

// compute vector toward waypoint
float wx = (path[curr_waypoint].x - car.varsF[0]);
float wy = (path[curr_waypoint].y - car.varsF[1]);

// normalize wx, wy
float length = Fast_Distance_2D(wx+0.5,wy+0.5);
wx/=length;
wy/=length;

// compute angle in radians
float car_angle = ((-90+car.curr_frame*22.5)*PI)/180;

// compute velocity vector of car (use look up for cos, sin in real life
float xv = cos(car_angle);
float yv = sin(car_angle);

// draw vectors
if (vector_display_on==1)
   {
   DDraw_Lock_Back_Surface();
   Draw_Line16(car.varsF[0],car.varsF[1], path[curr_waypoint].x, path[curr_waypoint].y, 
              250, back_buffer, back_lpitch); 

   Draw_Line16(car.varsF[0],car.varsF[1], car.varsF[0]+16*xv,car.varsF[1]+16*yv,
              246, back_buffer, back_lpitch); 
   DDraw_Unlock_Back_Surface();
   } // end if

// now turn car into waypoint direction, get sign of cross product
// between each vector
float sign_cross = (xv*wy - yv*wx);


if (ai_on)
{
// test the sign to determine which way to turn plus a little slosh
if (sign_cross > 0.3)
   {
   if (++car.curr_frame > 15)
      car.curr_frame = 0;   

   sprintf(buffer,"AI Turning RIGHT", sign_cross);
   Draw_Text_GDI(buffer,320, 460,RGB(255,255,255),lpddsback);

   } // end if
else
if (sign_cross < -0.3)
   {
   if (--car.curr_frame < 0 )
      car.curr_frame = 15;   

   sprintf(buffer,"AI Turning LEFT", sign_cross);
   Draw_Text_GDI(buffer,320, 460,RGB(255,255,255),lpddsback);

   } // end if
else
   {
   sprintf(buffer,"AI Turning 0", sign_cross);
   Draw_Text_GDI(buffer,320, 460,RGB(255,255,255),lpddsback);

   } // end else
} // end if
else
   {
   sprintf(buffer,"AI Disabled by user override", sign_cross);
   Draw_Text_GDI(buffer,320, 460,RGB(255,255,255),lpddsback);
   } // end if


// adjust floating position
car.varsF[0] += (xv*speed);
car.varsF[1] += (yv*speed);

// test for off screen -- user could cause this
if (car.varsF[0] > screen_width)
    car.varsF[0] = 0;
else
if (car.varsF[0] < 0)
    car.varsF[0] = screen_width;

if (car.varsF[1] > screen_height)
    car.varsF[1] = 0;
else
if (car.varsF[1] < 0)
    car.varsF[1] = screen_height;

// position sprite on pixel center
car.x = (0.5+car.varsF[0] - 8);
car.y = (0.5+car.varsF[1] - 8);

// draw the car
Draw_BOB16(&car, lpddsback);

// show nearest waypoint
sprintf(buffer,"Nearest Waypoint %d", Find_Nearest_Waypoint(car.varsF[0],car.varsF[1]));
Draw_Text_GDI(buffer,64, 460,RGB(255,255,255),lpddsback);

sprintf(buffer,"(16-Bit Version) Path following demo. Use arrow keys to override AI, <D> to toggle info, and <ESC> to Exit.");
Draw_Text_GDI(buffer,8, 8,RGB(255,255,255),lpddsback);

// flip the surfaces
DDraw_Flip();

// sync to 30ish fps
Wait_Clock(30);

// check of user is trying to exit
if (KEY_DOWN(VK_ESCAPE) || keyboard_state[DIK_ESCAPE])
    {
    PostMessage(main_window_handle, WM_DESTROY,0,0);

    // stop all sounds
    DSound_Stop_All_Sounds();

    } // end if

// return success
return(1);

} // end Game_Main

//////////////////////////////////////////////////////////