//////////////////////////////////////////////////
// EZsketch (Etch-A-Sketch)
// main.c source code file
// Dennis R. Shows
// http://www.geocities.com/dr_shows
// dr_shows@yahoo.com
//////////////////////////////////////////////////

#define MULTIBOOT int __gba_multiboot;
MULTIBOOT

//define register for changing the video mode
#define REG_DISPCNT *(unsigned long*)0x4000000

//define RGB
#define RGB(r,g,b) ((((b)>>3)<<10)+(((g)>>3)<<5)+((r)>>3))

// define R_CTRLINPUT
#define MEM_IO				0x04000000	

typedef     unsigned short int      u16;

#define R_CTRLINPUT    *(volatile u16 *)(MEM_IO + 0x130)

#define F_CTRLINPUT_A_PRESSED        (~R_CTRLINPUT & 0x0001)
#define F_CTRLINPUT_B_PRESSED       ((~R_CTRLINPUT & 0x0002)>>1)
#define F_CTRLINPUT_SELECT_PRESSED  ((~R_CTRLINPUT & 0x0004)>>2)
#define F_CTRLINPUT_START_PRESSED   ((~R_CTRLINPUT & 0x0008)>>3)
#define F_CTRLINPUT_RIGHT_PRESSED   ((~R_CTRLINPUT & 0x0010)>>4)
#define F_CTRLINPUT_LEFT_PRESSED    ((~R_CTRLINPUT & 0x0020)>>5)
#define F_CTRLINPUT_UP_PRESSED      ((~R_CTRLINPUT & 0x0040)>>6)
#define F_CTRLINPUT_DOWN_PRESSED    ((~R_CTRLINPUT & 0x0080)>>7)
#define F_CTRLINPUT_R_PRESSED       ((~R_CTRLINPUT & 0x0100)>>8)
#define F_CTRLINPUT_L_PRESSED       ((~R_CTRLINPUT & 0x0200)>>9)

//video mode 3 = 240x160 16-bit
#define MODE_3 0x3

//use background 2
#define BG2_ENABLE 0x400

//create a pointer to the video buffer
unsigned short* videoBuffer = (unsigned short*)0x6000000;

//draw a pixel on the mode 3 video buffer
void DrawPixel3(int x, int y, unsigned short c)
{
	videoBuffer[y * 240 + x] = c;
}

//////////////////////////////////////////////////
// Function: main()
//////////////////////////////////////////////////
int main(void)
{
    int x, y;

    int delay;

    int dx,dy;
    dx = 120;
    dy = 80;

    //switch to video mode 3 (240x160 16-bit)
    REG_DISPCNT = (MODE_3 | BG2_ENABLE);

    //fill the screen with white pixels
    for (x = 20; x < 220; x++)
    {
        for (y = 20; y < 140; y++)
        {
            DrawPixel3(x, y, RGB(255,255,255));
        }
    }

//draw Etch-a-Scetch borders
//top
    for (x = 0; x < 240; x++)
    {
        for (y = 0; y < 20; y++)
        {
            DrawPixel3(x, y, RGB(255,0,0));
        }
    }
//bot
    for (x = 0; x < 240; x++)
    {
        for (y = 140; y < 160; y++)
        {
            DrawPixel3(x, y, RGB(255,0,0));
        }
    }
//left
    for (x = 0; x < 20; x++)
    {
        for (y = 20; y < 140; y++)
        {
            DrawPixel3(x, y, RGB(255,0,0));
        }
    }
//right
    for (x = 220; x < 240; x++)
    {
        for (y = 20; y < 140; y++)
        {
            DrawPixel3(x, y, RGB(255,0,0));
        }
    }

while(1){

//    if (F_CTRLINPUT_A_PRESSED) //keyboard z
//    {

      if (F_CTRLINPUT_RIGHT_PRESSED)
      {
         DrawPixel3(dx, dy, RGB(0,0,0));
        if (dx<219) dx++;
      }

      if (F_CTRLINPUT_LEFT_PRESSED)
      {
         DrawPixel3(dx, dy, RGB(0,0,0));
        if (dx>20) dx--;
      }

      if (F_CTRLINPUT_UP_PRESSED)
      {
         DrawPixel3(dx, dy, RGB(0,0,0));
        if (dy>20) dy--;
      }

      if (F_CTRLINPUT_DOWN_PRESSED)
      {
         DrawPixel3(dx, dy, RGB(0,0,0));
        if (dy<139) dy++;
      }

//    } //close if A pressed

          //slow down the program
        delay = 50000;
        while (delay--);

} //close while
    return 0;
} //close main

/*
Extensions
Challenge 1: Change the color, shape, or size of the Ecth-a-Sketch.  Add knobs.
Challenge 2: Move the "DrawPixel3(dx, dy, RGB(0,0,0));" into a funtion and
    call it when needed.
Challenge 3: Add a funtion for changing the color or the pixels depending on what button
    is pressed.  Add an eraser.
Challenge 4: Make a cursor so the user can tell where the pointer is.  Change the size of
    of the thickness of the line.
Challenge 5: Put the "fill the screen with white pixels" and "draw Etch-a-Scetch" sections
    in a function and have a menu pop up for erasing the screen.  Be sure to save the
    screen before covering it up.
Challenge 6: Remove the Etch-a-Sketch border and intead put a image on the screen to
    draw over.  See http://www.geocities.com/dr_shows/EZsketch.bmp for an image.
Challenge 7: Make the knobs appear to move when the user draws.
For answers to challenges, more demos, help, etc. go to http://www.geocities.com/dr_shows
*/