diff --git a/dotscape b/dotscape
index 23c1f32..0b83805 100755
Binary files a/dotscape and b/dotscape differ
diff --git a/fcore/app-with.sml b/fcore/app-with.sml
index dafb00a..364677e 100644
--- a/fcore/app-with.sml
+++ b/fcore/app-with.sml
@@ -19,62 +19,6 @@ struct
           Vector.tabulate (maxPoints, fn _ => {r = 0, g = 0, b = 0, a = 0}))
     end
 
-  fun squares (app, newSquares) =
-    let
-      val
-        { mode
-        , squares
-        , arrowX
-        , arrowY
-        , canvasWidth
-        , canvasHeight
-        , windowWidth
-        , windowHeight
-        , xClickPoints
-        , yClickPoints
-
-        , showGraph
-        , mouseX
-        , mouseY
-        , openFilePath
-        , fileBrowser
-        , fileBrowserIdx
-        , r
-        , g
-        , b
-        , a
-        , layer
-        , layerTree
-        , modalNum
-        } = app
-    in
-      { mode = mode
-      , squares = newSquares
-      , arrowX = arrowX
-      , arrowY = arrowY
-      , canvasWidth = canvasWidth
-      , canvasHeight = canvasHeight
-      , windowWidth = windowWidth
-      , windowHeight = windowHeight
-      , xClickPoints = xClickPoints
-      , yClickPoints = yClickPoints
-
-      , showGraph = showGraph
-      , mouseX = mouseX
-      , mouseY = mouseY
-      , openFilePath = openFilePath
-      , fileBrowser = fileBrowser
-      , fileBrowserIdx = fileBrowserIdx
-      , r = r
-      , g = g
-      , b = b
-      , a = a
-      , layer = layer
-      , layerTree = layerTree
-      , modalNum = modalNum
-      }
-    end
-
   fun arrowX (app, arrowX) =
     let
       val
diff --git a/fcore/move-mode.sml b/fcore/move-mode.sml
index ed7eae9..b7134f9 100644
--- a/fcore/move-mode.sml
+++ b/fcore/move-mode.sml
@@ -20,17 +20,19 @@ struct
         , canvasHeight
         , windowWidth
         , windowHeight
-        , squares
+        , layerTree
         , xClickPoints
         , yClickPoints
         , ...
         } = model
 
       val maxSide = Int.max (canvasWidth, canvasHeight)
+      val grid = LayerTree.flatten (maxSide, layerTree)
+
       val squares = CollisionTree.toTriangles
         ( windowWidth
         , windowHeight
-        , squares
+        , grid
         , maxSide
         , canvasWidth
         , canvasHeight
@@ -51,71 +53,61 @@ struct
   fun makeBlankXAxis length =
     Vector.tabulate (length, fn _ => makeBlankYAxis length)
 
-  fun moveImageUp (model: app_type) =
+  fun finishMove (model: app_type, newGrid) =
     let
-      val {squares, ...} = model
-
-      val squares =
-        Vector.mapi
-          (fn (_, yAxis) =>
-             Vector.mapi
-               (fn (yIdx, pixel) =>
-                  if yIdx = Vector.length yAxis - 1 then blankPixel
-                  else Vector.sub (yAxis, yIdx + 1)) yAxis) squares
-
-      val model = AppWith.squares (model, squares)
+      val {layer, layerTree, arrowX, arrowY, ...} = model
+      val layerTree = LayerTree.insert (layer, newGrid, layerTree)
+      val model = AppWith.layerTree (model, layerTree, arrowX, arrowY)
     in
       getDrawMsg model
     end
 
-  fun moveImageDown (model: app_type) =
+  fun moveImage (model: app_type, fMove) =
     let
-      val {squares, ...} = model
-
-      val squares =
-        Vector.mapi
-          (fn (_, yAxis) =>
-             Vector.mapi
-               (fn (yIdx, pixel) =>
-                  if yIdx = 0 then blankPixel else Vector.sub (yAxis, yIdx - 1))
-               yAxis) squares
-
-      val model = AppWith.squares (model, squares)
+      val {layer, layerTree, ...} = model
     in
-      getDrawMsg model
+      case LayerTree.get (layer, layerTree) of
+        SOME grid => finishMove (model, fMove grid)
+      | NONE => (model, [])
     end
 
-  fun moveImageLeft (model: app_type) =
-    let
-      val {squares, ...} = model
+  fun helpMoveImageUp grid =
+    Vector.mapi
+      (fn (_, yAxis) =>
+         Vector.mapi
+           (fn (yIdx, pixel) =>
+              if yIdx = Vector.length yAxis - 1 then blankPixel
+              else Vector.sub (yAxis, yIdx + 1)) yAxis) grid
 
-      val squares =
-        Vector.mapi
-          (fn (idx, yAxis) =>
-             if idx + 1 = Vector.length squares then
-               makeBlankYAxis (Vector.length squares)
-             else
-               Vector.sub (squares, idx + 1)) squares
+  fun moveImageUp (model: app_type) = moveImage (model, helpMoveImageUp)
 
-      val model = AppWith.squares (model, squares)
-    in
-      getDrawMsg model
-    end
+  fun helpMoveImageDown grid =
+    Vector.mapi
+      (fn (_, yAxis) =>
+         Vector.mapi
+           (fn (yIdx, pixel) =>
+              if yIdx = 0 then blankPixel else Vector.sub (yAxis, yIdx - 1))
+           yAxis) grid
 
-  fun moveImageRight (model: app_type) =
-    let
-      val {squares, ...} = model
+  fun moveImageDown (model: app_type) = moveImage (model, helpMoveImageDown)
 
-      val squares =
-        Vector.mapi
-          (fn (idx, yAxis) =>
-             if idx = 0 then makeBlankYAxis (Vector.length squares)
-             else Vector.sub (squares, idx - 1)) squares
+  fun helpMoveImageLeft grid =
+    Vector.mapi
+      (fn (idx, yAxis) =>
+         if idx + 1 = Vector.length grid then
+           makeBlankYAxis (Vector.length grid)
+         else
+           Vector.sub (grid, idx + 1)) grid
 
-      val model = AppWith.squares (model, squares)
-    in
-      getDrawMsg model
-    end
+  fun moveImageLeft (model: app_type) = moveImage (model, helpMoveImageLeft)
+
+  fun helpMoveImageRight grid =
+    Vector.mapi
+      (fn (idx, yAxis) =>
+         if idx = 0 then makeBlankYAxis (Vector.length grid)
+         else Vector.sub (grid, idx - 1)) grid
+
+  fun moveImageRight (model: app_type) = moveImage (model, helpMoveImageRight)
 
   fun enterNormalMode model =
     let val model = AppWith.mode (model, AppType.NORMAL_MODE)