unsigned short r256table[255];
unsigned char r256index;

#define xcells 59
#define ycells 39

#define xlinelen (xcells<<1)
#define ylinelen (ycells<<1)

#define xmax (xlinelen-1)
#define ymax (ylinelen-1)

unsigned char maze[ylinelen+1][xlinelen+1];

#define STACK_TOP ((unsigned short*)0x2040000)

unsigned short *mazestack = STACK_TOP;

void r256init() {
	unsigned int i,j,msb;
	j=42424;
	for(i=0;i<256;i++){
		r256table[i]=(unsigned short)(j=j*0x103);
	}
	msb=0x8000;
	j=0;
	for(i=0;i<16;i++) {
		j=i*5+3;
		r256table[j]|=msb;
		r256table[j+1]&=~msb;
		msb>>=1;
	}
}

unsigned short r256() {
	unsigned short r;
	r=r256table[(r256index+103)&255]^r256table[r256index];
	r256table[r256index++]=r;
	return r;
}	

void DrawMaze() {
	int x,y;
	for(x=0;x<120*160;x++)
		((unsigned int*)0x6000000)[x]=0x7FFF7FFF;
	for(y=0;y<ylinelen;y+=2){
		for(x=0;x<xlinelen;x+=2) {
			((unsigned short *)0x6000000)[(y*240+x)*2]=0;
			if(maze[y][x+1]==1) {
				((unsigned short *)0x6000000)[(y*240+x)*2+1]=0;
				((unsigned short *)0x6000000)[(y*240+x)*2+2]=0;
				((unsigned short *)0x6000000)[(y*240+x)*2+3]=0;
			}
			if(maze[y+1][x]==1) {
				((unsigned short *)0x6000000)[(y*240+x)*2+240]=0;
				((unsigned short *)0x6000000)[(y*240+x)*2+480]=0;
				((unsigned short *)0x6000000)[(y*240+x)*2+720]=0;
			}
			if(maze[y+1][x+1]==1) {
				((unsigned short *)0x6000000)[(y*240+x)*2+482]=0;
			}
		}
		((unsigned short *)0x6000000)[(y*240+x)*2]=0;
		if(maze[y+1][x]==1) {
			((unsigned short *)0x6000000)[(y*240+x)*2+240]=0;
			((unsigned short *)0x6000000)[(y*240+x)*2+480]=0;
			((unsigned short *)0x6000000)[(y*240+x)*2+720]=0;
		}
	}
	for(x=0;x<xlinelen;x+=2) {
		((unsigned short *)0x6000000)[(y*240+x)*2]=0;
		if(maze[y][x+1]==1) {
			((unsigned short *)0x6000000)[(y*240+x)*2+1]=0;
			((unsigned short *)0x6000000)[(y*240+x)*2+2]=0;
			((unsigned short *)0x6000000)[(y*240+x)*2+3]=0;
		}
	}
	((unsigned short *)0x6000000)[(y*240+x)*2]=0;
}

void Dig(int x, int y) {
	mazestack -= 2;
	mazestack[0] = x;
	mazestack[1] = y;
}

void BackTrack(int *x, int *y) {
	*x = mazestack[0];
	*y = mazestack[1];
	mazestack += 2;
}
	
void DigMaze(int x,int y) {
	int todo;

	Dig(x,y);
	while(1) {
		maze[y][x]=0;
		todo=0;
		if(x>1) todo|=maze[y][x-2];
		if(x<xmax) todo|=maze[y][x+2];
		if(y>1) todo|=maze[y-2][x];
		if(y<ymax) todo|=maze[y+2][x];
		if(todo!=0) {
			switch(r256()>>14){
			case 0:
				if(x>1) {
					if(maze[y][x-2]!=0) {
						maze[y][x-1]=0;
						x -= 2;
						Dig(x,y);
					}
				}
				break;
			case 1:
				if(x<xmax) {
					if(maze[y][x+2]!=0) {
						maze[y][x+1]=0;
						x += 2;
						Dig(x,y);
					}
				}
				break;
			case 2:
				if(y>1) {
					if(maze[y-2][x]!=0) {
						maze[y-1][x]=0;
						y -= 2;
						Dig(x,y);
					}
				}
				break;
			case 3:
				if(y<ymax) {
					if(maze[y+2][x]!=0) {
						maze[y+1][x]=0;
						y += 2;
						Dig(x,y);
					}
				}
				break;
			}
		} else { 
			if(mazestack < STACK_TOP) BackTrack(&x, &y);
			else return; 
		}
		//DrawMaze();
	}
}

void AgbMain(){
	r256init();
	*(unsigned short*)0x4000000=0x403;
	*(unsigned short*)0x4000004=0;
	int x,y;
	for(x=0;x<120*160;x++)
		((unsigned int*)0x6000000)[x]=0;
	while(1) {
		do{
			for(y=0;y<=ylinelen;y++)
				for(x=0;x<=xlinelen;x++)
					maze[y][x]=1;
			x=((r256()*xcells)>>15)|1; y=((r256()*ycells)>>15)|1;
			DigMaze(x,y);
			maze[((r256()*ycells)>>15)|1][xlinelen]=0;
			x=0;
			y=((r256()*ycells)>>15)|1;
			maze[y][0]=0;
			DrawMaze();
			((unsigned short *)0x6000000)[(y*240+x)*2]=0x01FF;
			((unsigned short *)0x6000000)[(y*240+x)*2+1]=0x01FF;
			((unsigned short *)0x6000000)[(y*240+x)*2+2]=0x01FF;
			x++;
			maze[y][x]=2;
		} while(((*(volatile unsigned short*)0x4000130) & 8)!=0);
		while(((*(volatile unsigned short*)0x4000130) & 255)!=255) {}
		while(x<xlinelen) {
			while(((*(volatile unsigned short*)0x4000130) & 0xF0)==0xF0) {}
			switch ((*(volatile unsigned short*)0x4000130) & 0xF0) {
			case 0xE0: //Right
				do{
					if(maze[y][x+1]==1) break;
					x+=2;
					if(x>=xlinelen) break;
					if(maze[y][x]==0) {
						((unsigned short *)0x6000000)[(y*240+x)*2]=0x01FF;
						((unsigned short *)0x6000000)[(y*240+x)*2-1]=0x01FF;
						((unsigned short *)0x6000000)[(y*240+x)*2-2]=0x01FF;
						((unsigned short *)0x6000000)[(y*240+x)*2-3]=0x01FF;
						maze[y][x]=2;
					} else {
						((unsigned short *)0x6000000)[(y*240+x)*2-1]=0x7FFF;
						((unsigned short *)0x6000000)[(y*240+x)*2-2]=0x7FFF;
						((unsigned short *)0x6000000)[(y*240+x)*2-3]=0x7FFF;
						((unsigned short *)0x6000000)[(y*240+x)*2-4]=0x7FFF;
						maze[y][x-2]=0;
					}
				} while(maze[y-1][x]==1 && maze[y+1][x]==1);
				break;
			case 0xD0: //Left
				do{
					if(x<=1 || maze[y][x-1]==1) break;
					x-=2;
					if(maze[y][x]==0) {
						((unsigned short *)0x6000000)[(y*240+x)*2]=0x01FF;
						((unsigned short *)0x6000000)[(y*240+x)*2+1]=0x01FF;
						((unsigned short *)0x6000000)[(y*240+x)*2+2]=0x01FF;
						((unsigned short *)0x6000000)[(y*240+x)*2+3]=0x01FF;
						maze[y][x]=2;
					} else {
						((unsigned short *)0x6000000)[(y*240+x)*2+1]=0x7FFF;
						((unsigned short *)0x6000000)[(y*240+x)*2+2]=0x7FFF;
						((unsigned short *)0x6000000)[(y*240+x)*2+3]=0x7FFF;
						((unsigned short *)0x6000000)[(y*240+x)*2+4]=0x7FFF;
						maze[y][x+2]=0;
					}
				} while(maze[y-1][x]==1 && maze[y+1][x]==1);
				break;
			case 0xB0: //Up
				do{
					if(y<=1 || maze[y-1][x]==1) break;
					y-=2;
					if(maze[y][x]==0) {
						((unsigned short *)0x6000000)[(y*240+x)*2]=0x01FF;
						((unsigned short *)0x6000000)[(y*240+x)*2+240]=0x01FF;
						((unsigned short *)0x6000000)[(y*240+x)*2+480]=0x01FF;
						((unsigned short *)0x6000000)[(y*240+x)*2+720]=0x01FF;
						maze[y][x]=2;
					} else {
						((unsigned short *)0x6000000)[(y*240+x)*2+240]=0x7FFF;
						((unsigned short *)0x6000000)[(y*240+x)*2+480]=0x7FFF;
						((unsigned short *)0x6000000)[(y*240+x)*2+720]=0x7FFF;
						((unsigned short *)0x6000000)[(y*240+x)*2+960]=0x7FFF;
						maze[y+2][x]=0;
					}
				} while(maze[y][x-1]==1 && maze[y][x+1]==1);
				break;
			case 0x70: //Down
				do{
					if(y>=ylinelen-1 || maze[y+1][x]==1) break;
					y+=2;
					if(maze[y][x]==0) {
						((unsigned short *)0x6000000)[(y*240+x)*2]=0x01FF;
						((unsigned short *)0x6000000)[(y*240+x)*2-240]=0x01FF;
						((unsigned short *)0x6000000)[(y*240+x)*2-480]=0x01FF;
						((unsigned short *)0x6000000)[(y*240+x)*2-720]=0x01FF;
						maze[y][x]=2;
					} else {
						((unsigned short *)0x6000000)[(y*240+x)*2-240]=0x7FFF;
						((unsigned short *)0x6000000)[(y*240+x)*2-480]=0x7FFF;
						((unsigned short *)0x6000000)[(y*240+x)*2-720]=0x7FFF;
						((unsigned short *)0x6000000)[(y*240+x)*2-960]=0x7FFF;
						maze[y-2][x]=0;
					}
				} while(maze[y][x-1]==1 && maze[y][x+1]==1);
				break;
			}
			while(((*(volatile unsigned short*)0x4000130) & 0xF0)!=0xF0) {}
		}
		((unsigned short *)0x6000000)[(y*240+x)*2]=0x01FF;
		((unsigned short *)0x6000000)[(y*240+x)*2-1]=0x01FF;
		((unsigned short *)0x6000000)[(y*240+x)*2-2]=0x01FF;
		((unsigned short *)0x6000000)[(y*240+x)*2-3]=0x01FF;
		while(((*(volatile unsigned short*)0x4000130) & 8)!=0) {}
	}
}