begin title screen by adding title screen type

fcore/game-type.sml

@@ -1,6 +1,6 @@
 signature GAME_TYPE =
 sig
-  datatype mode = LEVEL of LevelType.level_type
+  datatype mode = LEVEL of LevelType.level_type | TITLE of TitleType.title_type
 
   type game_type = {userKeys: CoreKey.user_key, mode: mode}
 
@@ -9,12 +9,12 @@ end
 
 structure GameType :> GAME_TYPE =
 struct
-  datatype mode = LEVEL of LevelType.level_type
+  datatype mode = LEVEL of LevelType.level_type | TITLE of TitleType.title_type
 
   type game_type = {userKeys: CoreKey.user_key, mode: mode}
 
   fun init userKeys =
-    let val mode = LEVEL LevelType.initial
+    let val mode = TITLE TitleType.initial
     in {mode = mode, userKeys = userKeys}
     end
 end

fcore/game-update.sml

@@ -12,6 +12,10 @@ struct
             let val level = LevelUpdate.update (level, input)
             in LEVEL level
             end
+        | TITLE title =>
+            let val title = TitleUpdate.update (title, input)
+            in TITLE title
+            end
     in
       {mode = mode, userKeys = userKeys}
     end

fcore/level/level-update.sml

@@ -1,6 +1,6 @@
 structure LevelUpdate =
 struct
-  fun update (game, input) =
+  fun update (level, input) =
     let
       val
         { player
@@ -11,9 +11,9 @@ struct
         , enemies
         , graph
         , fallingEnemies
-        } = game
+        } = level
 
-      val player = Player.runPhysicsAndInput (game, input)
+      val player = Player.runPhysicsAndInput (level, input)
 
       val enemyTree = Enemy.generateTree enemies
       val player = Player.checkEnemyCollisions (player, enemies, enemyTree)

fcore/title/title-type.sml

@@ -0,0 +1,17 @@
+signature TITLE_TYPE =
+sig
+  datatype focus = START_BUTTON
+
+  type title_type = {focus: focus}
+
+  val initial: title_type
+end
+
+structure TitleType :> TITLE_TYPE =
+struct
+  datatype focus = START_BUTTON
+
+  type title_type = {focus: focus}
+
+  val initial = {focus = START_BUTTON}
+end

fcore/title/title-update.sml

@@ -0,0 +1,6 @@
+structure TitleUpdate =
+struct
+  open TitleType
+
+  fun update (titleState, input) = titleState
+end