diff --git a/dotscape b/dotscape
index 0b83805..2a56919 100755
Binary files a/dotscape and b/dotscape differ
diff --git a/fcore/app-with.sml b/fcore/app-with.sml
index 364677e..8c217e6 100644
--- a/fcore/app-with.sml
+++ b/fcore/app-with.sml
@@ -875,7 +875,7 @@ struct
       }
     end
 
-  fun canvasWidth (app: app_type, newCanvasWidth) =
+  fun canvasWidth (app: app_type, newCanvasWidth, newLayerTree) =
     let
       val
         { mode
@@ -900,11 +900,10 @@ struct
         , b
         , a
         , layer
-        , layerTree
+        , layerTree = _
         , modalNum
         } = app
 
-      val squares = changeSquaresSize (squares, newCanvasWidth, canvasHeight)
       val arrowX = Int.min (arrowX, newCanvasWidth)
       val (xClickPoints, yClickPoints) =
         ClickPoints.generate
@@ -932,12 +931,12 @@ struct
       , b = b
       , a = a
       , layer = layer
-      , layerTree = layerTree
+      , layerTree = newLayerTree
       , modalNum = 0
       }
     end
 
-  fun canvasHeight (app: app_type, newCanvasHeight) =
+  fun canvasHeight (app: app_type, newCanvasHeight, newLayerTree) =
     let
       val
         { mode
@@ -962,11 +961,10 @@ struct
         , b
         , a
         , layer
-        , layerTree
+        , layerTree = _
         , modalNum
         } = app
 
-      val squares = changeSquaresSize (squares, canvasWidth, newCanvasHeight)
       val arrowY = Int.min (arrowY, newCanvasHeight)
       val (xClickPoints, yClickPoints) =
         ClickPoints.generate
@@ -994,7 +992,7 @@ struct
       , b = b
       , a = a
       , layer = layer
-      , layerTree = layerTree
+      , layerTree = newLayerTree
       , modalNum = 0
       }
     end
diff --git a/fcore/normal-mode.sml b/fcore/normal-mode.sml
index 76840e7..a2c428f 100644
--- a/fcore/normal-mode.sml
+++ b/fcore/normal-mode.sml
@@ -251,12 +251,18 @@ struct
 
   fun selectCursorColour (model: app_type) =
     let
-      val {squares, arrowX, arrowY, ...} = model
-      val yAxis = Vector.sub (squares, arrowX)
-      val {r, g, b, a} = Vector.sub (yAxis, arrowY)
-      val model = AppWith.cursorColour (model, r, g, b, a)
+      val {layer, layerTree, arrowX, arrowY, ...} = model
     in
-      (model, [])
+      case LayerTree.get (layer, layerTree) of
+        SOME grid =>
+          let
+            val yAxis = Vector.sub (grid, arrowX)
+            val {r, g, b, a} = Vector.sub (yAxis, arrowY)
+            val model = AppWith.cursorColour (model, r, g, b, a)
+          in
+            (model, [])
+          end
+      | NONE => (model, [])
     end
 
   fun updateCanvas (model, canvasWidth, canvasHeight) =
@@ -266,10 +272,10 @@ struct
         , arrowY
         , windowWidth
         , windowHeight
-        , squares
         , xClickPoints
         , yClickPoints
         , showGraph
+        , layerTree
         , ...
         } = model
 
@@ -278,6 +284,8 @@ struct
         if showGraph then GraphLines.generate model else Vector.fromList []
 
       val maxSide = Int.max (canvasWidth, canvasHeight)
+      val squares = LayerTree.flatten (maxSide, layerTree)
+
       val squares = CollisionTree.toTriangles
         ( windowWidth
         , windowHeight
@@ -298,9 +306,13 @@ struct
 
   fun updateCanvasWidth model =
     let
-      val newCanvasWidth = #modalNum model
-      val (model as {canvasWidth, canvasHeight, ...}) =
-        AppWith.canvasWidth (model, newCanvasWidth)
+      val {modalNum, layerTree, canvasHeight, ...} = model
+      val newCanvasWidth = modalNum
+
+      val maxSide = Int.max (newCanvasWidth, canvasHeight)
+      val layerTree = LayerTree.changeGridSize (maxSide, layerTree)
+
+      val model = AppWith.canvasWidth (model, newCanvasWidth, layerTree)
       val {canvasWidth, canvasHeight, ...} = model
     in
       updateCanvas (model, canvasWidth, canvasHeight)
@@ -308,8 +320,13 @@ struct
 
   fun updateCanvasHeight model =
     let
-      val newCanvasHeight = #modalNum model
-      val model = AppWith.canvasHeight (model, newCanvasHeight)
+      val {modalNum, layerTree, canvasWidth, ...} = model
+      val newCanvasHeight = modalNum
+
+      val maxSide = Int.max (newCanvasHeight, canvasWidth)
+      val layerTree = LayerTree.changeGridSize (maxSide, layerTree)
+
+      val model = AppWith.canvasHeight (model, newCanvasHeight, layerTree)
       val {canvasWidth, canvasHeight, ...} = model
     in
       updateCanvas (model, canvasWidth, canvasHeight)