/****************************************/
/*			Virtual Screen				*/
/****************************************/


#include "gba.h"
#include "back.h"
#include "back.c"
void init_screen(void);
void wait(int);

hword* bcolor = (hword*) BG_PALETTE;

// Screen definition
screen plane[ 1 ] = {
	{ (hword*) VRAM_MAP(16), (hword*) VRAM_TILE(0), 0, 0 }	// Page 0
};

int main() {
	int key, xoff = 0, yoff = 0; // Key status, x-offset, y-offset

	// Initialize screen
	init_screen();

	// Key scan loop
	while (1) {
		key = gba_reg(KEY_STA);
		if ((key & KEY_ALL) == KEY_ALL)
			continue;
		key = key ^ KEY_ALL;

		if (key & KEY_UP) {
			if (yoff == 0)
				continue;
			yoff--;
			gba_reg(BG0_VOFFSET) = yoff;
		}
		else if (key & KEY_DOWN) {
			if (yoff == (256 - (20 * 8)))
				continue;
			yoff++;
			gba_reg(BG0_VOFFSET) = yoff;
		}
		else if (key & KEY_RIGHT) {
			if (xoff == (256 - (30 * 8)))
				continue;
			xoff++;
			gba_reg(BG0_HOFFSET) = xoff;
		}
		else if (key & KEY_LEFT) {
			if (xoff == 0)
				continue;
			xoff--;
			gba_reg(BG0_HOFFSET) = xoff;
		}
		wait(80);
	};
}

void init_screen(void) {

	int i;

	// Initialize palette
	for (i = 0; i < 256; i++)
		bcolor[ i ] = back_pal[ i ];

	// Setup tiles for background
	for (i = 0; i < 8 * 2 * 32; i++)
		plane[ 0 ].tile[ i ] = back_data[ 2 * i ] + (back_data[ 2 * i + 1] << 8);

	// Setup the map for background
	for (i = 0; i < 32 * 32; i++)
		plane[ 0 ].map[ i ] = back[ i ];

	// Start LCD display
	gba_reg(BG0_CTL)  =	LCD_SIZE00  |
							LCD_COLOR256 |
							LCD_BGTILE(0) |
							LCD_BGMAP(16);
	gba_reg(LCD_CTL) =	LCD_BG0 |
							LCD_MODE0;
 }

void wait(int time) {

	int i, j;

	for (i = 0; i < time; i++)
		for (j = 0; j < time; j++) ;
}