diff --git a/temp-squares/app-with.sml b/temp-squares/app-with.sml
index 66b52f1..6a91f58 100644
--- a/temp-squares/app-with.sml
+++ b/temp-squares/app-with.sml
@@ -110,7 +110,7 @@ struct
       }
     end
 
-  fun arrowX (app, arrowY) =
+  fun arrowY (app, arrowY) =
     let
       val
         { mode
diff --git a/temp-squares/graph-lines.sml b/temp-squares/graph-lines.sml
new file mode 100644
index 0000000..e69425f
--- /dev/null
+++ b/temp-squares/graph-lines.sml
@@ -0,0 +1,142 @@
+signature GRAPH_LINES =
+sig
+  val generate: AppType.app_type -> Real32.real vector
+end
+
+structure GraphLines :> GRAPH_LINES =
+struct
+      (* 
+   * This function only produces the desired result 
+   * when the window is a square and has the aspect ratio 1:1.
+   * This is because the function assumes it can use 
+   * the same position coordinates both horizontally and vertically.
+   *)
+  fun helpGenGraphLinesSquare (pos: Real32.real, limit, acc) =
+    if pos >= limit then
+      Vector.concat acc
+    else
+      let
+        val vec = 
+          #[ (* x = _.1 *) 
+             pos - 0.001, ~1.0
+           , pos + 0.001, ~1.0
+           , pos + 0.001, 1.0
+
+           , pos + 0.001, 1.0
+           , pos - 0.001, 1.0
+           , pos - 0.001, ~1.0
+
+             (* y = _.1 *)
+           , ~1.0, pos - 0.001
+           , ~1.0, pos + 0.001
+           , 1.0, pos + 0.001
+
+           , 1.0, pos + 0.001
+           , 1.0, pos - 0.001
+           , ~1.0, pos - 0.001 
+           ]
+        val acc = vec :: acc
+        val nextPos = pos + 0.1
+      in
+        helpGenGraphLinesSquare (nextPos, limit, acc)
+      end
+
+  fun helpGenGraphLinesHorizontal
+    (pos, xClickPoints, acc, halfWidth, yMin, yMax) =
+    if pos = Vector.length xClickPoints then
+      acc
+    else
+      let
+        val curX = Vector.sub (xClickPoints, pos)
+        val ndc = (curX - halfWidth) / halfWidth
+        val acc =
+           #[
+              ndc - 0.001, yMin
+            , ndc + 0.001, yMin
+            , ndc + 0.001, yMax
+
+            , ndc + 0.001, yMax
+            , ndc - 0.001, yMax
+            , ndc - 0.001, yMin
+            ] :: acc
+      in
+        helpGenGraphLinesHorizontal
+          (pos + 1, xClickPoints, acc, halfWidth, yMin, yMax)
+      end
+
+  fun helpGenGraphLinesVertical (pos, yClickPoints, acc, halfHeight, xMin, xMax) =
+    if pos = Vector.length yClickPoints then
+      acc
+    else
+      let
+        val curY = Vector.sub (yClickPoints, pos)
+        val ndc = (curY - halfHeight) / halfHeight
+        val acc =
+            #[
+               xMin, ndc - 0.001
+             , xMin, ndc + 0.001
+             , xMax, ndc + 0.001
+
+             , xMax, ndc + 0.001
+             , xMax, ndc - 0.001
+             , xMin, ndc - 0.001 
+             ] :: acc
+      in
+        helpGenGraphLinesVertical
+          (pos + 1, yClickPoints, acc, halfHeight, xMin, xMax)
+      end
+
+  fun helpGenerate (windowWidth, windowHeight, xClickPoints, yClickPoints) =
+    if windowWidth = windowHeight then
+      helpGenGraphLinesSquare (~1.0, 1.0, [])
+    else if windowWidth > windowHeight then
+      let
+        val difference = windowWidth - windowHeight
+        val offset = difference div 2
+
+        val halfWidth = Real32.fromInt (windowWidth div 2)
+        val halfHeight = Real32.fromInt (windowHeight div 2)
+
+        val start = offset - (windowWidth div 2)
+        val start = Real32.fromInt start / halfWidth
+
+        val finish = (windowWidth - offset) - (windowWidth div 2)
+        val finish = Real32.fromInt finish / halfWidth
+
+        val lines = helpGenGraphLinesHorizontal
+          (0, xClickPoints, [], halfWidth, ~1.0, 1.0)
+        val lines = helpGenGraphLinesVertical
+          (0, yClickPoints, lines, halfHeight, start, finish)
+      in
+        Vector.concat lines
+      end
+    else
+      (* windowWidth < windowHeight *)
+      let
+        val difference = windowHeight - windowWidth
+        val offset = difference div 2
+
+        val halfWidth = Real32.fromInt (windowWidth div 2)
+        val halfHeight = Real32.fromInt (windowHeight div 2)
+
+        val start = offset - (windowHeight div 2)
+        val start = Real32.fromInt start / halfHeight
+
+        val finish = (windowHeight - offset) - (windowHeight div 2)
+        val finish = Real32.fromInt finish / halfHeight
+
+        val lines = helpGenGraphLinesHorizontal
+          (0, xClickPoints, [], halfWidth, start, finish)
+        val lines = helpGenGraphLinesVertical
+          (0, yClickPoints, lines, halfHeight, ~1.0, 1.0)
+      in
+        Vector.concat lines
+      end
+
+  fun generate (app: AppType.app_type) = 
+    let
+      val {windowWidth, windowHeight, xClickPoints, yClickPoints, ...} = app
+    in
+      helpGenerate (windowWidth, windowHeight, xClickPoints, yClickPoints)
+    end
+end
diff --git a/temp-squares/temp.mlb b/temp-squares/temp.mlb
index 3621bf2..0e3346d 100644
--- a/temp-squares/temp.mlb
+++ b/temp-squares/temp.mlb
@@ -6,3 +6,8 @@ click-points.sml
 app-init.sml
 app-with.sml
 
+ann
+  "allowVectorExps true"
+in
+  graph-lines.sml
+end