diff --git a/testbed.c b/testbed.c
index 5d37102..61cf5a5 100755
--- a/testbed.c
+++ b/testbed.c
@@ -386,11 +386,12 @@ int tifLoad(FILE *f, TifImageMeta_t meta, unsigned int *planeBuf, int maxY, int
   unsigned long offset;
   unsigned char rowData[MAX_WIDTH >> 1];
   unsigned int planeStride = (meta.width >> 4) * yRepeat;
-  unsigned int *b = planeBuf - 1;
-  unsigned int *g = b + planeStride;
-  unsigned int *r = g + planeStride;
-  unsigned int *i = r + planeStride;
-  unsigned int *m = i + planeStride;
+  unsigned int *bp = planeBuf;
+  unsigned int *gp = bp + planeStride;
+  unsigned int *rp = gp + planeStride;
+  unsigned int *ip = rp + planeStride;
+  unsigned int *mp = ip + planeStride;
+  unsigned char bv, gv, rv, iv;
 
   if (meta.width > MAX_WIDTH || (meta.width % 16) != 0 || planes < 4 || planes > 5) {
     return 0;
@@ -402,30 +403,31 @@ int tifLoad(FILE *f, TifImageMeta_t meta, unsigned int *planeBuf, int maxY, int
     fseek(f, offset, SEEK_SET);
 
     for (irow = 0; irow < meta.rowsPerStrip; irow ++) {
-      fread(rowData, 1, meta.width >> 1, f);
-      for (ipixelpair = 0; ipixelpair < meta.width >> 1; ipixelpair ++) {
+      int ipixelpairLim = meta.width >> 1;
+      fread(rowData, 1, ipixelpairLim, f);
+      bv = gv = rv = iv = 0;
+      for (ipixelpair = 0; ipixelpair < ipixelpairLim; ipixelpair ++) {
 	unsigned char pixelpair = rowData[ipixelpair];
 	int bpair = (pixelpair & 0x01) | (pixelpair & 0x10) >> 3;
 	int gpair = (pixelpair & 0x02) >> 1 | (pixelpair & 0x20) >> 4;
 	int rpair = (pixelpair & 0x04) >> 2 | (pixelpair & 0x40) >> 5;
 	int ipair = (pixelpair & 0x08) >> 3 | (pixelpair & 0x80) >> 6;
-	int shift = (ipixelpair % 8) << 1;
-	if (shift == 0) {
-	  *++b = bpair;
-	  *++g = gpair;
-	  *++r = rpair;
-	  *++i = ipair;
+	int shift = (3 - (ipixelpair % 4)) << 1;
+
+	bv |= bpair << shift;
+	gv |= gpair << shift;
+	rv |= rpair << shift;
+	iv |= ipair << shift;
+
+	if (shift == 0 || ipixelpair == ipixelpairLim - 1) {
+	  *bp++ = bv;
+	  *gp++ = gv;
+	  *rp++ = rv;
+	  *ip++ = iv;
 	  if (planes == 5) {
-	    *++m = bpair & gpair & rpair & ipair;
-	  }
-	} else {
-	  *b |= bpair << shift;
-	  *g |= gpair << shift;
-	  *r |= rpair << shift;
-	  *i |= ipair << shift;
-	  if (planes == 5) {
-	    *m |= (bpair & gpair & rpair & ipair) << shift;
+	    *mp++ = bv & gv & rv & iv;
 	  }
+	  bv = gv = rv = iv = 0;
 	}
       }
       y++;
@@ -433,10 +435,11 @@ int tifLoad(FILE *f, TifImageMeta_t meta, unsigned int *planeBuf, int maxY, int
 	return y;
       }
       if (y % yRepeat == 0) {
-	b += planeStride * (planes - 1);
-	g += planeStride * (planes - 1);
-	r += planeStride * (planes - 1);
-	i += planeStride * (planes - 1);
+	bp += planeStride * (planes - 1);
+	gp += planeStride * (planes - 1);
+	rp += planeStride * (planes - 1);
+	ip += planeStride * (planes - 1);
+	mp += planeStride * (planes - 1);
       }
     }
   }
@@ -509,11 +512,11 @@ int prepareBuffer(int pageX, int pageY) {
     unsigned int startY = screen.scrollY >> 4;
     unsigned char tile = screen.map[startX + pageX + ((startY + pageY) * screen.w)];
     unsigned char ibuffer = screen.nextBuffer;
-    screen.nextBuffer = nextBufferIndex(screen.nextBuffer);
+    screen.nextBuffer = nextBufferIndex(ibuffer);
     *dirty = ibuffer;
-    memcpy(screen.buffer[ibuffer], &screen.memTiles[tile * BUF_WSIZE], BUF_WSIZE);
+    memcpy(screen.buffer[ibuffer], &screen.memTiles[tile * BUF_WSIZE], BUF_WSIZE << 1);
     screen.bufferOffset[ibuffer] = screen.pageOffset[screen.currentPage]
-      + (pageX << 1) + (pageY * PAGE_STRIDE);
+      + (pageX << 1) + (pageY * PAGE_STRIDE * 16);
   }
   return *dirty;
 }
@@ -558,12 +561,10 @@ void drawSpriteToBuf(unsigned int *sprite, int pageX, int pageY, int shift, int
 }
 
 void drawSprite(unsigned int *sprite, int x, int y) {
-  unsigned int startX = screen.scrollX >> 4;
-  unsigned int startY = screen.scrollY >> 4;
-  int pageX = (x - startX) >> 4;
-  int pageY = (y - startY) >> 4;
-  int pageOffsetX = x - (pageX << 4);
-  int pageOffsetY = y - (pageY << 4);
+  int pageX = (x - (screen.scrollX & 0xfff0)) >> 4;
+  int pageY = (y - (screen.scrollY & 0xfff0)) >> 4;
+  int pageOffsetX = x & 0x0f;
+  int pageOffsetY = y & 0x0f;
 
   drawSpriteToBuf(sprite, pageX, pageY, pageOffsetX, pageOffsetY);
   drawSpriteToBuf(sprite, pageX + 1, pageY, pageOffsetX - 16, pageOffsetY);
@@ -572,15 +573,14 @@ void drawSprite(unsigned int *sprite, int x, int y) {
 }
 
 void scroll(int x, int y) {
-  unsigned int startX = screen.scrollX >> 4;
-  unsigned int startY = screen.scrollY >> 4;
   x = min(max(x, 0), (screen.w << 4) - 320);
   y = min(max(y, 0), (screen.h << 4) - 176);
-  screen.scrollX = x;
-  screen.scrollY = y;
-  if (startX != (x >> 4) || startY != (y >> 4)) {
+  if ((screen.scrollX & 0xfff0) != (x & 0xfff0) ||
+      (screen.scrollY & 0xfff0) != (y & 0xfff0)) {
     memset(screen.dirty, D_BGTILE, 2 * PAGE_TILES_COUNT);
   }
+  screen.scrollX = x;
+  screen.scrollY = y;
 }
 
 void drawScreen() {
@@ -695,7 +695,7 @@ int main() {
     if (keyPressed(K_RIGHT)) x += 1;
     if (keyPressed(K_UP))    y -= 1;
     if (keyPressed(K_DOWN))  y += 1;
-    scroll(x + 152, y + 90);
+    scroll(x - 152, y - 90);
     drawSprite(sprites[0], 50, 50);
     drawSprite(sprites[1], x, y);
     drawScreen();
diff --git a/testbed.exe b/testbed.exe
index ffcb4e3..b39e2c7 100755
Binary files a/testbed.exe and b/testbed.exe differ