diff --git a/src/cram.c b/src/cram.c
index 793b847..2944eca 100644
--- a/src/cram.c
+++ b/src/cram.c
@@ -110,6 +110,10 @@ typedef struct RectPackContext
 	Rect *freeRectangles;
 	int32_t freeRectangleCount;
 	int32_t freeRectangleCapacity;
+
+	Rect *newFreeRectangles;
+	int32_t newFreeRectangleCount;
+	int32_t newFreeRectangleCapacity;
 } RectPackContext;
 
 typedef struct PackScoreInfo
@@ -237,10 +241,14 @@ RectPackContext* Cram_Internal_InitRectPacker(uint32_t width, uint32_t height)
 	context->freeRectangles[0].h = height;
 	context->freeRectangleCount = 1;
 
+	context->newFreeRectangleCapacity = INITIAL_FREE_RECTANGLE_CAPACITY;
+	context->newFreeRectangles = Cram_malloc(sizeof(Rect) * context->freeRectangleCapacity);
+	context->newFreeRectangleCount = 0;
+
 	return context;
 }
 
-/* Uses the bottom left (Tetris) heuristic. */
+/* Uses the short side fit heuristic. */
 /* TODO: make the heuristic configurable? */
 void Cram_Internal_Score(
 	RectPackContext *context,
@@ -249,8 +257,8 @@ void Cram_Internal_Score(
 	PackScoreInfo *scoreInfo
 ) {
 	Rect *freeRect;
-	int32_t areaFit;
 	int32_t shortestSide;
+	int32_t longestSide;
 	int32_t i;
 
 	scoreInfo->score = INT32_MAX;
@@ -262,13 +270,13 @@ void Cram_Internal_Score(
 
 		if (freeRect->w >= width && freeRect->h >= height)
 		{
-			areaFit = freeRect->w * freeRect->h - width * height;
 			shortestSide = Cram_min(freeRect->w - width, freeRect->h - height);
+			longestSide = Cram_max(freeRect->w - width, freeRect->h - height);
 
-			if (areaFit < scoreInfo->score || (areaFit == scoreInfo->score && shortestSide < scoreInfo->secondaryScore))
+			if (shortestSide < scoreInfo->score || (shortestSide == scoreInfo->score && longestSide < scoreInfo->secondaryScore))
 			{
-				scoreInfo->score = areaFit;
-				scoreInfo->secondaryScore = shortestSide;
+				scoreInfo->score = shortestSide;
+				scoreInfo->secondaryScore = longestSide;
 				scoreInfo->x = freeRect->x;
 				scoreInfo->y = freeRect->y;
 			}
@@ -287,45 +295,63 @@ static inline uint8_t Cram_Internal_Contains(Rect* a, Rect* b)
 void Cram_Internal_PruneRects(RectPackContext* context)
 {
 	int32_t i, j;
-	Rect* a;
-	Rect* b;
 
-	for (i = context->freeRectangleCount - 1; i >= 0; i -= 1)
+	for (i = 0; i < context->freeRectangleCount; i += 1)
 	{
-		a = &context->freeRectangles[i];
-
-		for (j = context->freeRectangleCount - 1; j > i; j -= 1)
+		for (j = 0; j < context->newFreeRectangleCount;)
 		{
-			b = &context->freeRectangles[j];
-
-			if (Cram_Internal_Contains(b, a))
+			if (Cram_Internal_Contains(&context->freeRectangles[i], &context->newFreeRectangles[j]))
 			{
 				/* plug the hole */
-				context->freeRectangles[j] = context->freeRectangles[context->freeRectangleCount - 1];
-				context->freeRectangleCount -= 1;
-				break;
+				context->newFreeRectangles[j] = context->newFreeRectangles[context->newFreeRectangleCount - 1];
+				context->newFreeRectangleCount -= 1;
 			}
-
-			if (Cram_Internal_Contains(a, b))
+			else
 			{
-				/* plug the hole */
-				context->freeRectangles[j] = context->freeRectangles[context->freeRectangleCount - 1];
-				context->freeRectangleCount -= 1;
+				j += 1;
 			}
 		}
 	}
-}
 
-static inline void Cram_Internal_AddFreeRect(RectPackContext *context, Rect rect)
-{
-	if (context->freeRectangleCount == context->freeRectangleCapacity)
+	if (context->freeRectangleCapacity < context->freeRectangleCount + context->newFreeRectangleCount)
 	{
-		context->freeRectangleCapacity *= 2;
+		context->freeRectangleCapacity = context->freeRectangleCount + context->newFreeRectangleCount;
 		context->freeRectangles = Cram_realloc(context->freeRectangles, sizeof(Rect) * context->freeRectangleCapacity);
 	}
 
-	context->freeRectangles[context->freeRectangleCount] = rect;
-	context->freeRectangleCount += 1;
+	for (i = 0; i < context->newFreeRectangleCount; i += 1)
+	{
+		context->freeRectangles[context->freeRectangleCount] = context->newFreeRectangles[i];
+		context->freeRectangleCount += 1;
+	}
+}
+
+static inline void Cram_Internal_AddNewFreeRect(RectPackContext *context, Rect rect)
+{
+	int32_t i;
+
+	for (i = context->newFreeRectangleCount - 1; i >= 0; i -= 1)
+	{
+		if (Cram_Internal_Contains(&context->newFreeRectangles[i], &rect))
+		{
+			return;
+		}
+
+		if (Cram_Internal_Contains(&rect, &context->newFreeRectangles[i]))
+		{
+			context->newFreeRectangles[i] = context->newFreeRectangles[context->newFreeRectangleCount - 1];
+			context->newFreeRectangleCount -= 1;
+		}
+	}
+
+	if (context->newFreeRectangleCount == context->newFreeRectangleCapacity)
+	{
+		context->newFreeRectangleCapacity *= 2;
+		context->newFreeRectangles = Cram_realloc(context->newFreeRectangles, sizeof(Rect) * context->newFreeRectangleCapacity);
+	}
+
+	context->newFreeRectangles[context->newFreeRectangleCount] = rect;
+	context->newFreeRectangleCount += 1;
 }
 
 uint8_t Cram_Internal_SplitRect(RectPackContext *context, Rect *rect, Rect *freeRect)
@@ -351,7 +377,7 @@ uint8_t Cram_Internal_SplitRect(RectPackContext *context, Rect *rect, Rect *free
 		{
 			newRect = *freeRect;
 			newRect.w = rect->x - freeRect->x;
-			Cram_Internal_AddFreeRect(context, newRect);
+			Cram_Internal_AddNewFreeRect(context, newRect);
 		}
 
 		/* Right side */
@@ -360,7 +386,7 @@ uint8_t Cram_Internal_SplitRect(RectPackContext *context, Rect *rect, Rect *free
 			newRect = *freeRect;
 			newRect.x = rect->x + rect->w;
 			newRect.w = freeRect->x + freeRect->w - (rect->x + rect->w);
-			Cram_Internal_AddFreeRect(context, newRect);
+			Cram_Internal_AddNewFreeRect(context, newRect);
 		}
 	}
 
@@ -371,7 +397,7 @@ uint8_t Cram_Internal_SplitRect(RectPackContext *context, Rect *rect, Rect *free
 		{
 			newRect = *freeRect;
 			newRect.h = rect->y - freeRect->y;
-			Cram_Internal_AddFreeRect(context, newRect);
+			Cram_Internal_AddNewFreeRect(context, newRect);
 		}
 
 		/* Bottom side */
@@ -380,7 +406,7 @@ uint8_t Cram_Internal_SplitRect(RectPackContext *context, Rect *rect, Rect *free
 			newRect = *freeRect;
 			newRect.y = rect->y + rect->h;
 			newRect.h = freeRect->y + freeRect->h - (rect->y + rect->h);
-			Cram_Internal_AddFreeRect(context, newRect);
+			Cram_Internal_AddNewFreeRect(context, newRect);
 		}
 	}
 
@@ -409,6 +435,8 @@ void Cram_Internal_PlaceRect(RectPackContext *context, Rect *rect)
 	}
 
 	Cram_Internal_PruneRects(context);
+
+	context->newFreeRectangleCount = 0;
 }
 
 /* Given rects with width and height, modifies rects with packed x and y positions. */