feat(scala): m09 input/app/runtime and m10 extensions with tests

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scala/solutions/Game.scala

@@ -1,12 +1,34 @@
 package snake
 
-/** m05 game: one `update` turns every action into a new state; replaying a game is a fold over its actions. */
+/**
+ * m05 game: one `update` turns every action into a new state; replaying a game is a fold over its actions.
+ * m10 adds pause, restart and a frame clock that speeds up as the score grows.
+ */
 object Game:
 
+  /** How many frames pass between game steps: 8 at first, one fewer every 3 points, never fewer than 2. */
+  def movesEvery(score: Int): Int = math.max(2, 8 - score / 3)
+
+  // One animation frame: count it, and every `movesEvery(score)`-th frame run a game step.
+  private def frame(state: GameState): GameState =
+    if state.status != Status.Playing then state
+    else
+      val counted = state.copy(frame = state.frame + 1)
+      if counted.frame % movesEvery(counted.score) == 0 then Spawn.tick(counted) else counted
+
+  // Pause and resume only make sense in those two statuses; a finished game stays finished.
+  private def togglePause(state: GameState): GameState = state.status match
+    case Status.Playing               => state.copy(status = Status.Paused)
+    case Status.Paused                => state.copy(status = Status.Playing)
+    case Status.GameOver | Status.Won => state
+
+  // Every case is listed (no `case _`): adding an Action later makes the compiler point here.
   def update(state: GameState, action: Action): GameState = action match
-    case Action.Tick       => Spawn.tick(state)
-    case Action.Turn(dir)  => Rules.turn(state, dir)
-    case _                 => state // TogglePause, Restart and Frame arrive in m10
+    case Action.Tick        => Spawn.tick(state)
+    case Action.Turn(dir)   => Rules.turn(state, dir)
+    case Action.TogglePause => togglePause(state)
+    case Action.Restart     => Spawn.newGame(state.seed)
+    case Action.Frame       => frame(state)
 
   def replay(state: GameState, actions: List[Action]): GameState = actions.foldLeft(state)(update)