@@ -41,13 +41,11 @@ readpixel(Uint8 *sprite, Uint8 h, Uint8 v)

 void

 clear(Ppu *p)

 {

-	int i, sz = p->height * p->width, rows = sz / 4;

-	for(i = 0; i < sz; ++i)

-		p->output[i] = p->colors[0];

-	for(i = 0; i < rows; i++) {

-		p->fg[i] = 0;

-		p->bg[i] = 0;

-	}

+	int sz = p->height * p->width, rows = sz / 4;

+	memset(p->output, p->colors[0], sz);

+	memset(p->fg, 0, rows);

+	memset(p->bg, 0, rows);

+	memset(p->up, 0xff, p->ver);

 }

 void

@@ -66,9 +64,12 @@ putcolors(Ppu *p, Uint8 *addr)

 void

 putpixel(Ppu *p, Uint8 *layer, Uint16 x, Uint16 y, Uint8 color)

 {

-	Uint16 row = (y % 8) + ((x / 8 + y / 8 * p->hor) * 16), col = 7 - (x % 8);

-	if(x >= p->hor * 8 || y >= p->ver * 8 || row > (p->hor * p->ver * 16) - 8)

+	if(x >= p->hor * 8 || y >= p->ver * 8)

+		return;

+	int row = (y % 8) + ((x / 8 + y / 8 * p->hor) * 16);

+	if(row > (p->hor * p->ver * 16) - 8)

 		return;

+	int col = 7 - (x % 8);

 	if(color == 0 || color == 2)

 		layer[row] &= ~(1UL << col);

 	else

@@ -77,6 +78,8 @@ putpixel(Ppu *p, Uint8 *layer, Uint16 x, Uint16 y, Uint8 color)

 		layer[row + 8] &= ~(1UL << col);

 	else

 		layer[row + 8] |= 1UL << col;

+

+	p->up[y / 8] |= 1<<(y % 8);

 }

 void

@@ -143,18 +146,25 @@ void

 drawppu(Ppu *p)

 {

 	Uint16 x, y;

-	for(y = 0; y < p->ver; ++y)

+	for(y = 0; y < p->ver; ++y) {

+		if(p->up[y] == 0)

+			continue;

 		for(x = 0; x < p->hor; ++x) {

 			Uint8 v, h;

 			Uint16 key = (y * p->hor + x) * 16;

-			for(v = 0; v < 8; v++)

+			for(v = 0; v < 8; v++) {

+				if((p->up[y] & (1<<v)) == 0)

+					continue;

 				for(h = 0; h < 8; h++) {

 					Uint8 color = readpixel(&p->fg[key], h, v);

 					if(color == 0)

 						color = readpixel(&p->bg[key], h, v);

 					drawpixel(p, x * 8 + p->pad + 7 - h, y * 8 + p->pad + v, color);

 				}

+			}

 		}

+		p->up[y] = 0;

+	}

 }

 int

@@ -171,6 +181,8 @@ initppu(Ppu *p, Uint8 hor, Uint8 ver, Uint8 pad)

 		return 0;

 	if(!(p->fg = malloc(p->width * p->height * sizeof(Uint8) / 4)))

 		return 0;

+	if(!(p->up = malloc(p->ver)))

+		return 0;

 	clear(p);

 	return 1;

 }

@@ -18,7 +18,7 @@ typedef unsigned short Uint16;

 typedef unsigned int Uint32;

 typedef struct Ppu {

-	Uint8 *bg, *fg;

+	Uint8 *bg, *fg, *up;

 	Uint16 hor, ver, pad, width, height;

 	Uint32 *output, colors[4];

 } Ppu;

@@ -86,6 +86,7 @@ quit(void)

 	free(ppu.output);

 	free(ppu.fg);

 	free(ppu.bg);

+	free(ppu.up);

 	SDL_UnlockAudioDevice(audio_id);

 	SDL_DestroyTexture(gTexture);

 	gTexture = NULL;