// Example from http://www.fampennings.nl/maarten/nds

#include "nds.h"

void memcpy16( u16 *dst, u16 *src, int numbytes ) {
  int i= numbytes / 2;
  while( i>0 ) { *dst= *src; dst++; src++; i--; }
}

u16 palette[]= {
  /*0*/ RGB15( 0, 0, 0), // index 0 is transparant
  /*1*/ RGB15(31,31,31), // white background
  /*2*/ RGB15( 0, 0,31), // blue for cell borders
  /*3*/ RGB15(31, 0, 0)  // red for dot
};

u8 tiles[] = { 
  // completely white
  1,1,1,1,1,1,1,1,
  1,1,1,1,1,1,1,1,
  1,1,1,1,1,1,1,1,
  1,1,1,1,1,1,1,1,
  1,1,1,1,1,1,1,1,
  1,1,1,1,1,1,1,1,
  1,1,1,1,1,1,1,1,
  1,1,1,1,1,1,1,1,
  // blue border
  0,0,0,0,0,0,0,2,
  0,0,0,0,0,0,0,2,
  0,0,0,0,0,0,0,2,
  0,0,0,0,0,0,0,2,
  0,0,0,0,0,0,0,2,
  0,0,0,0,0,0,0,2,
  0,0,0,0,0,0,0,2,
  2,2,2,2,2,2,2,2,
  // red dot
  0,0,0,0,0,0,0,0,
  0,0,0,0,0,0,0,0,
  0,0,3,3,3,0,0,0,
  0,0,3,3,3,0,0,0,
  0,0,3,3,3,0,0,0,
  0,0,0,0,0,0,0,0,
  0,0,0,0,0,0,0,0,
  0,0,0,0,0,0,0,0
};

int main(void) {
  int i;
  
  // Enable both screens and both 2D cores
  REG_POWERCNT= POWER_ALL_2D;
  
  // Set up main core
  DISPLAY_CR= MODE_0_2D | DISPLAY_BG0_ACTIVE | DISPLAY_BG1_ACTIVE;
  BG0_CR= BG_32x32 | BG_COLOR_256 | BG_MAP_BASE(0) | BG_TILE_BASE(1) | BG_PRIORITY_3; // back
  BG1_CR= BG_32x32 | BG_COLOR_256 | BG_MAP_BASE(1) | BG_TILE_BASE(1) | BG_PRIORITY_2;
  VRAM_A_CR= VRAM_ENABLE | VRAM_A_MAIN_BG;
  memcpy16( BG_PALETTE, palette, sizeof(palette) );
  memcpy16( (u16*)BG_TILE_RAM(1), (u16*)tiles, sizeof(tiles) );
  for( i=0; i<32*32; i++ ) ((u16*)BG_MAP_RAM(0))[i]= 0; // 0 is tile white
  for( i=0; i<32*32; i++ ) ((u16*)BG_MAP_RAM(1))[i]= 1; // 1 is tile cell

  // Set up sub core
  SUB_DISPLAY_CR= MODE_0_2D | DISPLAY_BG0_ACTIVE | DISPLAY_BG1_ACTIVE;
  SUB_BG0_CR= BG_32x32 | BG_COLOR_256 | BG_MAP_BASE(0) | BG_TILE_BASE(1) | BG_PRIORITY_3; // back
  SUB_BG1_CR= BG_32x32 | BG_COLOR_256 | BG_MAP_BASE(1) | BG_TILE_BASE(1) | BG_PRIORITY_2; 
  VRAM_C_CR= VRAM_ENABLE | VRAM_C_SUB_BG;
  memcpy16( BG_PALETTE_SUB, palette, sizeof(palette) );
  memcpy16( (u16*)BG_TILE_RAM_SUB(1), (u16*)tiles, sizeof(tiles) );
  for( i=0; i<32*32; i++ ) ((u16*)BG_MAP_RAM_SUB(0))[i]= 0; // 0 is tile white
  for( i=0; i<32*32; i++ ) ((u16*)BG_MAP_RAM_SUB(1))[i]= 2; // 2 is tile dot

  // Flush key buffer
  scanKeys();
  while( keysDown() ) scanKeys();
  
  int bg1_x= 0;
  int bg1_y= 0;
  while(1) {
    scanKeys();
  
    if( keysDown() & KEY_R ) REG_POWERCNT^= POWER_SWAP_LCDS;
    if( keysDown() & KEY_L ) REG_POWERCNT^= POWER_LCD; 

    if( keysDown() & KEY_X ) DISPLAY_CR^= DISPLAY_BG0_ACTIVE;
    if( keysDown() & KEY_Y ) DISPLAY_CR^= DISPLAY_BG1_ACTIVE;
      
    if( keysDown() & KEY_A ) SUB_DISPLAY_CR^= DISPLAY_BG0_ACTIVE;
    if( keysDown() & KEY_B ) SUB_DISPLAY_CR^= DISPLAY_BG1_ACTIVE;


    if( keysDown() & KEY_DOWN  ) { bg1_y--; BG1_Y0=bg1_y; SUB_BG1_Y0=bg1_y; }
    if( keysDown() & KEY_UP    ) { bg1_y++; BG1_Y0=bg1_y; SUB_BG1_Y0=bg1_y; }
    if( keysDown() & KEY_RIGHT ) { bg1_x--; BG1_X0=bg1_x; SUB_BG1_X0=bg1_x; }
    if( keysDown() & KEY_LEFT  ) { bg1_x++; BG1_X0=bg1_x; SUB_BG1_X0=bg1_x; }
  }

  return 0;
}