@@ -13,8 +13,9 @@ WITH REGARD TO THIS SOFTWARE.

 */

 /*

-      fgbg fgbg

-byte [0000 0000]

+pixel 0001 0002

+layer fgbg fgbg

+byte  1010 1010

 */

 static Uint8 blending[5][16] = {

@@ -27,42 +28,25 @@ static Uint8 blending[5][16] = {

 static void

 ppu_clear(Ppu *p)

 {

-	int x, y;

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

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

-			ppu_write(p, 0, x, y, 0);

-			ppu_write(p, 1, x, y, 0);

-		}

-	}

+	int row;

+	for(row = 0; row < p->height * p->width / 2; ++row)

+		p->pixels[row] = 0;

 }

 Uint8

 ppu_read(Ppu *p, Uint16 x, Uint16 y)

 {

 	int row = (x + y * p->width) / 0x2;

-

-	if(x % 2) {

-		if(p->pixels[row] & 0x0c) {

-			return (p->pixels[row] >> 0x2) & 0x3;

-		} else {

-			return (p->pixels[row] >> 0x0) & 0x3;

-		}

-	} else {

-		if(p->pixels[row] & 0xc0) {

-			return (p->pixels[row] >> 0x6) & 0x3;

-		} else {

-			return (p->pixels[row] >> 0x4) & 0x3;

-		}

-	}

-

-	return 0;

+	Uint8 seg = !(x & 0x1) << 2;

+	Uint8 byte = p->pixels[row] >> seg;

+	return (byte & 0x0c ? (byte >> 2) : byte) & 0x3;

 }

 void

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

 {

 	int row = (x + y * p->width) / 0x2;

-	int original = p->pixels[row];

+	Uint8 original = p->pixels[row];

 	Uint8 next = 0x0;

 	if(x % 2) {

 		if(layer) {

@@ -82,7 +66,8 @@ ppu_write(Ppu *p, Uint8 layer, Uint16 x, Uint16 y, Uint8 color)

 		}

 	}

 	p->pixels[row] = next;

-	p->reqdraw = 1;

+	if(original != next)

+		p->reqdraw = 1;

 }

 void

@@ -127,9 +112,7 @@ ppu_set_size(Ppu *p, Uint16 width, Uint16 height)

 	ppu_clear(p);

 	p->width = width;

 	p->height = height;

-	p->pixels = realloc(p->bg, p->width * p->height * sizeof(Uint8) * 2);

-	p->bg = p->pixels;

-	p->fg = p->pixels + (p->width * p->height * sizeof(Uint8));

+	p->pixels = realloc(p->pixels, p->width * p->height * sizeof(Uint8) / 2);

 	ppu_clear(p);

-	return p->bg && p->fg;

+	return !!p->pixels;

 }

@@ -22,7 +22,7 @@ typedef unsigned short Uint16;

 typedef unsigned int Uint32;

 typedef struct Ppu {

-	Uint8 *bg, *fg, *pixels, reqdraw;

+	Uint8 *pixels, reqdraw;

 	Uint16 width, height;

 } Ppu;