@@ -50,31 +50,31 @@ ppu_palette(Ppu *p, Uint8 *addr)

 	}

 	for(i = 4; i < 16; ++i)

 		p->palette[i] = p->palette[i / 4];

-	p->reqdraw = 1;

+	p->fg.reqdraw = p->bg.reqdraw = 1;

 }

 void

 ppu_resize(Ppu *p, Uint16 width, Uint16 height)

 {

 	Uint8 

-	*bg = realloc(p->bg, width * height), 

-	*fg = realloc(p->fg, width * height);

+	*bg = realloc(p->bg.p, width * height),

+	*fg = realloc(p->fg.p, width * height);

 	if(!bg || !fg)

 		return;

-	p->bg = bg;

-	p->fg = fg;

+	p->bg.p = bg;

+	p->fg.p = fg;

 	p->width = width;

 	p->height = height;

-	ppu_clear(p, p->bg);

-	ppu_clear(p, p->fg);

+	ppu_clear(p, &p->bg);

+	ppu_clear(p, &p->fg);

 }

 void

-ppu_clear(Ppu *p, Uint8 *layer)

+ppu_clear(Ppu *p, Layer *layer)

 {

 	Uint32 i, size = p->width * p->height;

 	for(i = 0; i < size; ++i)

-		layer[i] = 0x00;

+		layer->p[i] = 0x00;

 }

 void

@@ -82,25 +82,25 @@ ppu_redraw(Ppu *p, Uint32 *screen)

 {

 	Uint32 i, size = p->width * p->height;

 	for(i = 0; i < size; ++i)

-		screen[i] = p->palette[p->fg[i] ? p->fg[i] : p->bg[i]];

-	p->reqdraw = 0;

+		screen[i] = p->palette[p->fg.p[i] ? p->fg.p[i] : p->bg.p[i]];

+	p->fg.reqdraw = p->bg.reqdraw = 0;

 }

 void

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

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

 {

 	if(x < p->width && y < p->height) {

-		Uint32 row = (x + y * p->width);

-		Uint8 prev = layer[row];

+		Uint32 i = (x + y * p->width);

+		Uint8 prev = layer->p[i];

 		if(color != prev) {

-			layer[row] = color;

-			p->reqdraw = 1;

+			layer->p[i] = color;

+			layer->reqdraw = 1;

 		}

 	}

 }

 void

-ppu_1bpp(Ppu *p, Uint8 *layer, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy)

+ppu_1bpp(Ppu *p, Layer *layer, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy)

 {

 	Uint16 v, h;

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

@@ -116,7 +116,7 @@ ppu_1bpp(Ppu *p, Uint8 *layer, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, U

 }

 void

-ppu_2bpp(Ppu *p, Uint8 *layer, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy)

+ppu_2bpp(Ppu *p, Layer *layer, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy)

 {

 	Uint16 v, h;

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

@@ -140,24 +140,24 @@ ppu_debug(Ppu *p, Uint8 *stack, Uint8 wptr, Uint8 rptr, Uint8 *memory)

 	for(i = 0; i < 0x20; ++i) {

 		x = ((i % 8) * 3 + 1) * 8, y = (i / 8 + 1) * 8, b = stack[i];

 		/* working stack */

-		ppu_1bpp(p, p->fg, x, y, font[(b >> 4) & 0xf], 1 + (wptr == i) * 0x7, 0, 0);

-		ppu_1bpp(p, p->fg, x + 8, y, font[b & 0xf], 1 + (wptr == i) * 0x7, 0, 0);

+		ppu_1bpp(p, &p->fg, x, y, font[(b >> 4) & 0xf], 1 + (wptr == i) * 0x7, 0, 0);

+		ppu_1bpp(p, &p->fg, x + 8, y, font[b & 0xf], 1 + (wptr == i) * 0x7, 0, 0);

 		y = 0x28 + (i / 8 + 1) * 8;

 		b = memory[i];

 		/* return stack */

-		ppu_1bpp(p, p->fg, x, y, font[(b >> 4) & 0xf], 3, 0, 0);

-		ppu_1bpp(p, p->fg, x + 8, y, font[b & 0xf], 3, 0, 0);

+		ppu_1bpp(p, &p->fg, x, y, font[(b >> 4) & 0xf], 3, 0, 0);

+		ppu_1bpp(p, &p->fg, x + 8, y, font[b & 0xf], 3, 0, 0);

 	}

 	/* return pointer */

-	ppu_1bpp(p, p->fg, 0x8, y + 0x10, font[(rptr >> 4) & 0xf], 0x2, 0, 0);

-	ppu_1bpp(p, p->fg, 0x10, y + 0x10, font[rptr & 0xf], 0x2, 0, 0);

+	ppu_1bpp(p, &p->fg, 0x8, y + 0x10, font[(rptr >> 4) & 0xf], 0x2, 0, 0);

+	ppu_1bpp(p, &p->fg, 0x10, y + 0x10, font[rptr & 0xf], 0x2, 0, 0);

 	/* guides */

 	for(x = 0; x < 0x10; ++x) {

-		ppu_write(p, p->fg, x, p->height / 2, 2);

-		ppu_write(p, p->fg, p->width - x, p->height / 2, 2);

-		ppu_write(p, p->fg, p->width / 2, p->height - x, 2);

-		ppu_write(p, p->fg, p->width / 2, x, 2);

-		ppu_write(p, p->fg, p->width / 2 - 0x10 / 2 + x, p->height / 2, 2);

-		ppu_write(p, p->fg, p->width / 2, p->height / 2 - 0x10 / 2 + x, 2);

+		ppu_write(p, &p->fg, x, p->height / 2, 2);

+		ppu_write(p, &p->fg, p->width - x, p->height / 2, 2);

+		ppu_write(p, &p->fg, p->width / 2, p->height - x, 2);

+		ppu_write(p, &p->fg, p->width / 2, x, 2);

+		ppu_write(p, &p->fg, p->width / 2 - 0x10 / 2 + x, p->height / 2, 2);

+		ppu_write(p, &p->fg, p->width / 2, p->height / 2 - 0x10 / 2 + x, 2);

 	}

 }

@@ -20,18 +20,23 @@ typedef unsigned char Uint8;

 typedef unsigned short Uint16;

 typedef unsigned int Uint32;

+typedef struct Layer {

+	Uint8 *p;

+	Uint8 reqdraw;

+} Layer;

+

 typedef struct Ppu {

-	Uint8 *fg, *bg, reqdraw;

+	Layer fg, bg;

 	Uint16 width, height;

 	Uint32 palette[16];

 } Ppu;

 void ppu_palette(Ppu *p, Uint8 *addr);

 void ppu_resize(Ppu *p, Uint16 width, Uint16 height);

-void ppu_clear(Ppu *p, Uint8 *layer);

+void ppu_clear(Ppu *p, Layer *layer);

 void ppu_redraw(Ppu *p, Uint32 *screen);

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

-void ppu_1bpp(Ppu *p, Uint8 *layer, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy);

-void ppu_2bpp(Ppu *p, Uint8 *layer, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy);

+void ppu_write(Ppu *p, Layer *layer, Uint16 x, Uint16 y, Uint8 color);

+void ppu_1bpp(Ppu *p, Layer *layer, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy);

+void ppu_2bpp(Ppu *p, Layer *layer, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy);

 void ppu_debug(Ppu *p, Uint8 *stack, Uint8 wptr, Uint8 rptr, Uint8 *memory);

@@ -105,7 +105,7 @@ set_zoom(Uint8 scale)

 	if(!gWindow)

 		return;

 	set_window_size(gWindow, (ppu.width + PAD * 2) * zoom, (ppu.height + PAD * 2) * zoom);

-	ppu.reqdraw = 1;

+	ppu.fg.reqdraw = ppu.bg.reqdraw = 1;

 }

 static int

@@ -128,7 +128,7 @@ set_size(Uint16 width, Uint16 height, int is_resize)

 		return error("SDL_UpdateTexture", SDL_GetError());

 	if(is_resize)

 		set_window_size(gWindow, (ppu.width + PAD * 2) * zoom, (ppu.height + PAD * 2) * zoom);

-	ppu.reqdraw = 1;

+	ppu.fg.reqdraw = ppu.bg.reqdraw = 1;

 	return 1;

 }

@@ -293,7 +293,7 @@ screen_deo(Device *d, Uint8 port)

 		Uint16 x = peek16(d->dat, 0x8);

 		Uint16 y = peek16(d->dat, 0xa);

 		Uint8 layer = d->dat[0xe] & 0x40;

-		ppu_write(&ppu, layer ? ppu.fg : ppu.bg, x, y, d->dat[0xe] & 0x3);

+		ppu_write(&ppu, layer ? &ppu.fg : &ppu.bg, x, y, d->dat[0xe] & 0x3);

 		if(d->dat[0x6] & 0x01) poke16(d->dat, 0x8, x + 1); /* auto x+1 */

 		if(d->dat[0x6] & 0x02) poke16(d->dat, 0xa, y + 1); /* auto y+1 */

 		break;

@@ -304,10 +304,10 @@ screen_deo(Device *d, Uint8 port)

 		Uint8 layer = d->dat[0xf] & 0x40;

 		Uint8 *addr = &d->mem[peek16(d->dat, 0xc)];

 		if(d->dat[0xf] & 0x80) {

-			ppu_2bpp(&ppu, layer ? ppu.fg : ppu.bg, x, y, addr, d->dat[0xf] & 0xf, d->dat[0xf] & 0x10, d->dat[0xf] & 0x20);

+			ppu_2bpp(&ppu, layer ? &ppu.fg : &ppu.bg, x, y, addr, d->dat[0xf] & 0xf, d->dat[0xf] & 0x10, d->dat[0xf] & 0x20);

 			if(d->dat[0x6] & 0x04) poke16(d->dat, 0xc, peek16(d->dat, 0xc) + 16); /* auto addr+16 */

 		} else {

-			ppu_1bpp(&ppu, layer ? ppu.fg : ppu.bg, x, y, addr, d->dat[0xf] & 0xf, d->dat[0xf] & 0x10, d->dat[0xf] & 0x20);

+			ppu_1bpp(&ppu, layer ? &ppu.fg : &ppu.bg, x, y, addr, d->dat[0xf] & 0xf, d->dat[0xf] & 0x10, d->dat[0xf] & 0x20);

 			if(d->dat[0x6] & 0x04) poke16(d->dat, 0xc, peek16(d->dat, 0xc) + 8); /* auto addr+8 */

 		}

 		if(d->dat[0x6] & 0x01) poke16(d->dat, 0x8, x + 8); /* auto x+8 */

@@ -467,7 +467,7 @@ doctrl(Uxn *u, SDL_Event *event, int z)

 	case SDLK_LEFT: flag = 0x40; break;

 	case SDLK_RIGHT: flag = 0x80; break;

 	case SDLK_F1: if(z) set_zoom(zoom > 2 ? 1 : zoom + 1); break;

-	case SDLK_F2: if(z) devsystem->dat[0xe] = !devsystem->dat[0xe]; ppu_clear(&ppu, ppu.fg); break;

+	case SDLK_F2: if(z) devsystem->dat[0xe] = !devsystem->dat[0xe]; ppu_clear(&ppu, &ppu.fg); break;

 	case SDLK_F3: if(z) capture_screen(); break;

 	case SDLK_AC_BACK:

 	case SDLK_F4: if(z) restart(u); break;

@@ -550,7 +550,7 @@ run(Uxn *u)

 		}

 	breakout:

 		uxn_eval(u, devscreen->vector);

-		if(ppu.reqdraw || devsystem->dat[0xe])

+		if(ppu.fg.reqdraw || ppu.bg.reqdraw || devsystem->dat[0xe])

 			redraw(u);

 		if(!BENCH) {

 			elapsed = (SDL_GetPerformanceCounter() - begin) / (double)SDL_GetPerformanceFrequency() * 1000.0f;