// 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;
  
  // All four backgrounds are text/tiles (mode 0), but only use bg0, bg1, bg2
  DISPLAY_CR= MODE_0_2D | DISPLAY_BG0_ACTIVE | DISPLAY_BG1_ACTIVE | DISPLAY_BG2_ACTIVE;
  
  // BGs are 32x32, 256 colors
  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;
  BG2_CR= BG_32x32 | BG_COLOR_256 | BG_MAP_BASE(2) | BG_TILE_BASE(1) | BG_PRIORITY_1; // front
  
  // Allocate VRAM_A to the main core for BGs
  VRAM_A_CR= VRAM_ENABLE | VRAM_A_MAIN_BG;

  // Copying palette
  memcpy16( BG_PALETTE, palette, sizeof(palette) );

  // Copy down-slash tile
  memcpy16( (u16*)BG_TILE_RAM(1), (u16*)tiles, sizeof(tiles) );
  // Fill tile map
  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
  for( i=0; i<32*32; i++ ) ((u16*)BG_MAP_RAM(2))[i]= 2; // 2 is tile_dot

  // Flush key buffer
  scanKeys();
  while( keysDown() ) scanKeys();
  
  int bg2_x= 0;
  int bg2_y= 0;
  while(1) {
    scanKeys();
  
    if( keysDown() & KEY_R ) REG_POWERCNT^= POWER_SWAP_LCDS; // =lcdSwap()
    if( keysDown() & KEY_L ) REG_POWERCNT^= POWER_LCD; 

    if( keysDown() & KEY_X ) DISPLAY_CR^= DISPLAY_BG0_ACTIVE;
    if( keysDown() & KEY_A ) DISPLAY_CR^= DISPLAY_BG1_ACTIVE;
    if( keysDown() & KEY_B ) DISPLAY_CR^= DISPLAY_BG2_ACTIVE;

    if( keysDown() & KEY_Y ) { int p1=BG1_CR&3; int p2=BG2_CR&3; BG1_CR=(BG1_CR&~3)|p2;  BG2_CR=(BG2_CR&~3)|p1; }

    if( keysDown() & KEY_DOWN  ) { bg2_y--; BG2_Y0=bg2_y; }
    if( keysDown() & KEY_UP    ) { bg2_y++; BG2_Y0=bg2_y; }
    if( keysDown() & KEY_RIGHT ) { bg2_x--; BG2_X0=bg2_x; }
    if( keysDown() & KEY_LEFT  ) { bg2_x++; BG2_X0=bg2_x; }
  }

  return 0;
}