diff --git a/v5/desktop.py b/v5/desktop.py
index 5e1ddc2..7172dff 100644
--- a/v5/desktop.py
+++ b/v5/desktop.py
@@ -1,14 +1,6 @@
 import arcade
 from desktop_Platform import *
 
-def desktop_configureFixedWindow(p):
-  p.cell = 25
-  p.windowAntialiasing = False
-  p.windowHeight = 600
-  p.windowTitle = "OGS Memory"
-  p.windowWidth = 900
-#}
-
 def desktop_loadTextures(p):
   texs = []
   for (id, td) in enumerate(p.c.textureDescriptions):
diff --git a/v5/desktop_Platform.py b/v5/desktop_Platform.py
index e20374b..327f55a 100644
--- a/v5/desktop_Platform.py
+++ b/v5/desktop_Platform.py
@@ -3,11 +3,5 @@ import arcade
 class desktop_Platform:
   def __init__(self):
     self.c = None
-    self.cell = 0
     self.sprites = arcade.SpriteList()
     self.textures = []
-    self.windowAntialiasing = False
-    self.windowBackgroundColor = arcade.color.WHITE
-    self.windowHeight = 0
-    self.windowTitle = ""
-    self.windowWidth = 0
diff --git a/v5/desktop_Window.py b/v5/desktop_Window.py
index 9112cc9..238f08e 100644
--- a/v5/desktop_Window.py
+++ b/v5/desktop_Window.py
@@ -3,12 +3,12 @@ import arcade
 class desktop_Window(arcade.Window):
   def __init__(self, p):
     super().__init__(
-      p.windowWidth,
-      p.windowHeight,
-      p.windowTitle,
+      p.c.windowWidth,
+      p.c.windowHeight,
+      p.c.windowTitle,
     )
-    self.antialiasing = p.windowAntialiasing
-    arcade.set_background_color(p.windowBackgroundColor)
+    self.antialiasing = p.c.windowAntialiasing
+    self.background_color = arcade.color_from_hex_string(p.c.windowBackgroundColor)
     self.p = p
 
   def on_draw(self):
diff --git a/v5/gui.py b/v5/gui.py
index 0caa118..dc7e8d5 100644
--- a/v5/gui.py
+++ b/v5/gui.py
@@ -1,18 +1,22 @@
-from memory_Context import *
+from gui_aux import *
 from gui_TextureDescription import *
 from llm import *
+from memory_Context import *
 
-# Generate tile position
+# Generate textures descriptions
 #
 # Conditions:
-# 1. 
+# 1. tileImage or tileImageCount or tileImageHeight or tileImageWidth has just changed
+# 2. tileImage, tileImageCount, tileImageHeight, tileImageWidth are not empty
 @llm_by_value
-def gui_generateTilePositions(
+def gui_generateTextureDescriptions(
   c: memory_Context
 ) -> memory_Context:
   if (
-    c.recentField == "windowHeight" or
-    c.recentField == "windowWidth"
+    c.recentField == "tileImage" or
+    c.recentField == "tileImageCount" or
+    c.recentField == "tileImageHeight" or
+    c.recentField == "tileImageWidth"
   ):
     tds: list[gui_TextureDescription] = []
     for id in range(0, c.tileImageCount):
@@ -33,36 +37,48 @@ def gui_generateTilePositions(
   return c
 #}
 
-# Generate textures descriptions
+# Generate tile positions
 #
 # Conditions:
-# 1. tileImage or tileImageCount or tileImageHeight or tileImageWidth has just changed
-# 2. tileImage, tileImageCount, tileImageHeight, tileImageWidth are not empty
+# 1. cellSize, playField, windowHeight, or windowWidth has changed and none of them is zero
 @llm_by_value
-def gui_generateTextureDescriptions(
+def gui_generateTilePositions(
   c: memory_Context
 ) -> memory_Context:
   if (
-    c.recentField == "tileImage" or
-    c.recentField == "tileImageCount" or
-    c.recentField == "tileImageHeight" or
-    c.recentField == "tileImageWidth"
+    (
+      c.recentField != "cellSize" and
+      c.recentField != "playfieldSize" and
+      c.recentField != "windowHeight" and
+      c.recentField != "windowWidth"
+    ) or
+    (
+      c.cellSize == 0 or
+      c.playfieldSize == 0 or
+      c.windowHeight == 0 or
+      c.windowWidth == 0
+    )
   ):
-    tds: list[gui_TextureDescription] = []
-    for id in range(0, c.tileImageCount):
-      td = gui_createTextureDescription()
-      td.fileName = c.tileImage
-      td.height = c.tileImageHeight
-      td.width = c.tileImageWidth
-      td.x = id * c.tileImageWidth
-      td.y = 0
-      tds.append(td)
-    #}
-    c.textureDescriptions = tds
-    c.recentField = "textureDescriptions"
+    c.recentField = "none"
     return c
   #}
 
-  c.recentField = "none"
+  # Assume window size is an integer multiple of cell size.
+  widthInCells = c.windowWidth / c.cellSize
+  heightInCells = c.windowHeight / c.cellSize
+  positions = gui_aux_cellPositions(c.playfieldSize)
+
+  poss = []
+  for i in range(0, len(positions)):
+    p = positions[i]
+    pos = [p[0] * c.cellSize, p[1] * c.cellSize]
+    poss.append(pos)
+  #}
+  #tile.center_x = CELL * 2 + p[0] * CELL
+  #tile.center_y = HEIGHT - CELL * 2 - p[1] * CELL
+
+  c.tilePositions = poss
+  c.recentField = "tilePositions"
   return c
 #}
+
diff --git a/v5/gui_aux.py b/v5/gui_aux.py
new file mode 100644
index 0000000..e16004e
--- /dev/null
+++ b/v5/gui_aux.py
@@ -0,0 +1,46 @@
+
+# Generate positions in cell dimensions
+#
+# Conditions:
+# 1. 2x2 grid
+# 2. 4x4 grid
+def gui_aux_cellPositions(
+  size: int
+) -> [[int]]:
+  if (
+    size == 2
+  ):
+    return [
+      [14, 7],
+      [19, 7],
+      [14, 13],
+      [19, 13],
+    ]
+  #}
+
+  if (
+    size == 4
+  ):
+    return [
+      [9, 1],
+      [14, 1],
+      [19, 1],
+      [24, 1],
+
+      [9, 7],
+      [14, 7],
+      [19, 7],
+      [24, 7],
+
+      [9, 13],
+      [14, 13],
+      [19, 13],
+      [24, 13],
+
+      [9, 19],
+      [14, 19],
+      [19, 19],
+      [24, 19],
+    ]
+  #}
+#}
diff --git a/v5/gui_aux_test.py b/v5/gui_aux_test.py
new file mode 100644
index 0000000..7ed4fbf
--- /dev/null
+++ b/v5/gui_aux_test.py
@@ -0,0 +1,15 @@
+from gui_aux import *
+
+def test_gui_aux_cellPositions(
+) -> str:
+  items2x2 = gui_aux_cellPositions(2)
+  items4x4 = gui_aux_cellPositions(4)
+
+  if (
+    len(items2x2) == 4 and
+    len(items4x4) == 16
+  ):
+    return "OK: gui_aux_cellPositions"
+  #}
+  return "ERR: gui_aux_cellPositions"
+#}
diff --git a/v5/main-gui.py b/v5/main-gui.py
index 5682de9..194cc47 100644
--- a/v5/main-gui.py
+++ b/v5/main-gui.py
@@ -7,6 +7,7 @@ from desktop import *
 from desktop_Platform import *
 from desktop_Window import *
 from gui import *
+from gui_aux_test import *
 from gui_test import *
 from llm_test import *
 from llm_test_Python import *
@@ -49,6 +50,7 @@ print(cli_test_reportMatchedItems())
 print(cli_test_reportMismatchedItems())
 print(cli_test_reportVictory())
 
+print(test_gui_aux_cellPositions())
 print(test_gui_generateTextureDescriptions())
 
 ctrl = ctx_Controller(memory_createContext())
@@ -63,6 +65,7 @@ ctrl.registerFunctions([
 #  cli_selectItem,
 #  cli_showHelp,
   gui_generateTextureDescriptions,
+  gui_generateTilePositions,
   memory_detectMismatchedItems,
   memory_detectVictory,
   memory_generateConstPlayfield,
@@ -85,12 +88,18 @@ ctrl.registerCallback(copyContext)
 
 ctrl.set("didLaunch", True)
 ctrl.set("playfieldSize", 2)
+
+ctrl.set("cellSize", 25)
 ctrl.set("tileImage", "res/tiles.png")
 ctrl.set("tileImageCount", 3)
 ctrl.set("tileImageHeight", 100)
 ctrl.set("tileImageWidth", 75)
+ctrl.set("windowWidth", 900)
+ctrl.set("windowHeight", 600)
+ctrl.set("windowAntialiasing", False)
+ctrl.set("windowBackgroundColor", "#ffffff")
+ctrl.set("windowTitle", "OGS Memory")
 
-desktop_configureFixedWindow(p)
 desktop_loadTextures(p)
 
 wnd = desktop_Window(p)
diff --git a/v5/memory_Context.py b/v5/memory_Context.py
index 3fffb2b..db806cc 100644
--- a/v5/memory_Context.py
+++ b/v5/memory_Context.py
@@ -1,5 +1,6 @@
 class memory_Context:
   def __init__(self):
+    self.cellSize = 0
     self.didLaunch = False
     self.exit = False
     self.hiddenItems = []
@@ -23,6 +24,10 @@ class memory_Context:
     self.tileImageHeight = 0
     self.tileImageWidth = 0
     self.tilePositions = []
+    self.windowBackgroundColor = "#000000"
+    self.windowHeight = 0
+    self.windowTitle = ""
+    self.windowWidth = 0
     self.victory = False
 
   def field(self, fieldName):