diff --git a/src/tiles.c b/src/tiles.c
index 40b6d2c1..10e8edc2 100644
--- a/src/tiles.c
+++ b/src/tiles.c
@@ -195,7 +195,25 @@ int Tile_is_same(int t1, int t2)
 }
 
 ///
-int Tile_is_same_y(int t1, int t2)
+int Tile_is_same_flipped_x(int t1, int t2)
+{
+  byte *bmp1,*bmp2;
+  int y, x;
+  
+  bmp1 = Main_backups->Pages->Image[Main_current_layer].Pixels+(TILE_Y(t1))*Main_image_width+(TILE_X(t1));
+  bmp2 = Main_backups->Pages->Image[Main_current_layer].Pixels+(TILE_Y(t2))*Main_image_width+(TILE_X(t2)+Snap_width-1);
+  
+  for (y=0; y < Snap_height; y++)
+  {
+    for (x=0; x < Snap_width; x++)
+      if (*(bmp1+y*Main_image_width+x) != *(bmp2+y*Main_image_width-x))
+        return 0;
+  }
+  return 1;
+}
+
+///
+int Tile_is_same_flipped_y(int t1, int t2)
 {
   byte *bmp1,*bmp2;
   int y;
@@ -211,6 +229,25 @@ int Tile_is_same_y(int t1, int t2)
   return 1;
 }
 
+
+///
+int Tile_is_same_flipped_xy(int t1, int t2)
+{
+  byte *bmp1,*bmp2;
+  int y, x;
+  
+  bmp1 = Main_backups->Pages->Image[Main_current_layer].Pixels+(TILE_Y(t1))*Main_image_width+(TILE_X(t1));
+  bmp2 = Main_backups->Pages->Image[Main_current_layer].Pixels+(TILE_Y(t2)+Snap_height-1)*Main_image_width+(TILE_X(t2)+Snap_width-1);
+  
+  for (y=0; y < Snap_height; y++)
+  {
+    for (x=0; x < Snap_width; x++)
+      if (*(bmp1+y*Main_image_width+x) != *(bmp2-y*Main_image_width-x))
+        return 0;
+  }
+  return 1;
+}
+
 /// Create or update a tilemap based on current screen pixels.
 void Tilemap_create(void)
 {
@@ -293,7 +330,7 @@ void Tilemap_create(void)
     
     for (ref_tile=0; ref_tile<tile; ref_tile++)
     {
-      if (Main_tilemap[ref_tile].Previous<=ref_tile && Tile_is_same_y(ref_tile, tile))
+      if (Main_tilemap[ref_tile].Previous<=ref_tile && Tile_is_same_flipped_y(ref_tile, tile))
       {
         break; // stop loop on ref_tile
       }
@@ -305,7 +342,51 @@ void Tilemap_create(void)
       int last_tile=Main_tilemap[ref_tile].Previous;
       Main_tilemap[tile].Previous=last_tile;
       Main_tilemap[tile].Next=ref_tile;
-      Main_tilemap[tile].Flipped=Main_tilemap[ref_tile].Flipped ^ 2;
+      Main_tilemap[tile].Flipped=Main_tilemap[ref_tile].Flipped ^ TILE_FLIPPED_Y;
+      Main_tilemap[ref_tile].Previous=tile;
+      Main_tilemap[last_tile].Next=tile;
+      continue; // next tile
+    }
+    
+    // Try flipped-x comparison
+    
+    for (ref_tile=0; ref_tile<tile; ref_tile++)
+    {
+      if (Main_tilemap[ref_tile].Previous<=ref_tile && Tile_is_same_flipped_x(ref_tile, tile))
+      {
+        break; // stop loop on ref_tile
+      }
+    }
+    if (ref_tile<tile)
+    {
+      // New occurence of a known tile
+      // Insert at the end. classic doubly-linked-list.
+      int last_tile=Main_tilemap[ref_tile].Previous;
+      Main_tilemap[tile].Previous=last_tile;
+      Main_tilemap[tile].Next=ref_tile;
+      Main_tilemap[tile].Flipped=Main_tilemap[ref_tile].Flipped ^ TILE_FLIPPED_X;
+      Main_tilemap[ref_tile].Previous=tile;
+      Main_tilemap[last_tile].Next=tile;
+      continue; // next tile
+    }
+    
+    // Try flipped-xy comparison
+    
+    for (ref_tile=0; ref_tile<tile; ref_tile++)
+    {
+      if (Main_tilemap[ref_tile].Previous<=ref_tile && Tile_is_same_flipped_xy(ref_tile, tile))
+      {
+        break; // stop loop on ref_tile
+      }
+    }
+    if (ref_tile<tile)
+    {
+      // New occurence of a known tile
+      // Insert at the end. classic doubly-linked-list.
+      int last_tile=Main_tilemap[ref_tile].Previous;
+      Main_tilemap[tile].Previous=last_tile;
+      Main_tilemap[tile].Next=ref_tile;
+      Main_tilemap[tile].Flipped=Main_tilemap[ref_tile].Flipped ^ TILE_FLIPPED_XY;
       Main_tilemap[ref_tile].Previous=tile;
       Main_tilemap[last_tile].Next=tile;
       continue; // next tile
diff --git a/src/tiles.h b/src/tiles.h
index b718646e..875fc2bb 100644
--- a/src/tiles.h
+++ b/src/tiles.h
@@ -36,3 +36,10 @@ void Tilemap_draw(word x, word y, byte color);
 #define TILE_X(t) (((t)%Main_tilemap_width)*Snap_width+Snap_offset_X)
 #define TILE_Y(t) (((t)/Main_tilemap_width)*Snap_height+Snap_offset_Y)
 
+enum TILE_FLIPPED
+{
+  TILE_FLIPPED_NONE = 0,
+  TILE_FLIPPED_X = 1,
+  TILE_FLIPPED_Y = 2,
+  TILE_FLIPPED_XY = 3, // needs be TILE_FLIPPED_X|TILE_FLIPPED_Y
+};