Add some background color animation depending on level

GameScreen.java

@@ -1,17 +1,24 @@
+import java.awt.Color;
 import java.util.List;
 import java.util.ArrayList;
 
-class GameScreen
+class GameScreen implements LinearColorAnimator.AnimationListener
 {
+    private final static int LEVEL_TIME = 10;
+
     private final List<Drawable> _drawables;
     private final Bird _bird;
     private final World _world;
+    private final LinearColorAnimator _backgroundAnimator;
     private double _totalTime;
     private int _try;
+    private int _level;
 
     public GameScreen()
     {
         _drawables = new ArrayList<Drawable>();
+        _backgroundAnimator = new LinearColorAnimator(Color.BLACK, Color.WHITE, 1, this);
+        _backgroundAnimator.start();
         _bird = new Bird(this);
         _world = new World(this);
         _totalTime = 0;
@@ -25,10 +32,24 @@ class GameScreen
     {
         _bird.update(elapsed);
         _world.update(elapsed);
+        _backgroundAnimator.update(elapsed);
         _totalTime += elapsed;
         System.out.print("\r" + _try + " - Time survived: " + (int)(_totalTime * 1e-3) + "s, " +
                 "speed: " + (int)_world.getSpeed() + "px/s");
 
+        if (_totalTime / (LEVEL_TIME * 1e3) > _level + 1)
+        {
+            ++_level;
+            // Would be nice to add some more levels with different colors
+            if (_level == 1)
+            {
+                _world.setObstacleColor("grau");
+                _backgroundAnimator.setStart(Color.WHITE);
+                _backgroundAnimator.setEnd(Color.BLACK);
+                _backgroundAnimator.start();
+            }
+        }
+
         Rectangle birdRect = _bird.getRect();
         if (_world.checkCollision(_bird.getRect())
                 || birdRect.getY() + birdRect.getHeight() > TurtleWelt.HEIGHT
@@ -36,16 +57,32 @@ class GameScreen
         {
             System.out.print("\n");
             ++_try;
-            _totalTime = 0;
+            _totalTime = _level = 0;
             _bird.reset();
             _world.reset();
+
+            // If the background is currently not white, smoothly animate it back
+            if (_backgroundAnimator.getCurrentColor().getRGB() != Color.WHITE.getRGB())
+            {
+                _backgroundAnimator.setStart(_backgroundAnimator.getCurrentColor());
+                _backgroundAnimator.setEnd(Color.WHITE);
+                _backgroundAnimator.start();
+            }
         }
     }
 
+    public void onAnimationFinished()
+    {
+        if (_backgroundAnimator.getEnd().getRGB() == Color.BLACK.getRGB())
+        {
+            _world.setObstacleColor("weiss");
+        }
+    }
 
     public void draw(Turtle turtle, double elapsed)
     {
-        TurtleWelt.globaleWelt.bildschirmEinfaerben(255, 255, 255);
+        Color bg = _backgroundAnimator.getCurrentColor();
+        TurtleWelt.globaleWelt.bildschirmEinfaerben(bg.getRed(), bg.getGreen(), bg.getBlue());
         for (Drawable d : _drawables)
         {
             d.draw(turtle, elapsed);

LinearColorAnimator.java

@@ -0,0 +1,115 @@
+import java.awt.Color;
+
+class LinearColorAnimator
+{
+    private Color _start, _end;
+    private final AnimationListener _listener;
+    private int _duration;
+    private double _elapsed;
+    private boolean _started;
+    private boolean _finished;
+
+    /*
+     * @param duration Duration in seconds
+     */
+    public LinearColorAnimator(Color start, Color end, int duration, AnimationListener listener)
+    {
+        _start = start;
+        _end = end;
+        _duration = duration;
+        _listener = listener;
+    }
+
+    /*
+     * @param elapsed Elapsed time since last call in ms
+     */
+    public void update(double elapsed)
+    {
+        if (_started)
+        {
+            _elapsed += elapsed * 1e-3;
+
+            if (_elapsed > _duration)
+            {
+                _started = false;
+                _finished = true;
+                if (_listener != null)
+                {
+                    _listener.onAnimationFinished();
+                }
+            }
+        }
+    }
+
+    public void start()
+    {
+        _started = true;
+        _finished = false;
+        _elapsed = 0;
+    }
+
+    public void reset()
+    {
+        _started = _finished = false;
+        _elapsed = 0;
+    }
+
+    public void setStart(Color c)
+    {
+        _start = c;
+    }
+
+    public void setEnd(Color c)
+    {
+        _end = c;
+    }
+
+    public void setDuration(int duration)
+    {
+        _duration = duration;
+    }
+
+    public boolean hasStarted()
+    {
+        return _started;
+    }
+
+    public boolean hasFinished()
+    {
+        return _finished;
+    }
+
+    public Color getStart()
+    {
+        return _start;
+    }
+
+    public Color getEnd()
+    {
+        return _end;
+    }
+
+    public Color getCurrentColor()
+    {
+        if (_finished)
+        {
+            return _end;
+        }
+        if (!_started)
+        {
+            return _start;
+        }
+        int diffR = _end.getRed() - _start.getRed();
+        int diffG = _end.getGreen() - _start.getGreen();
+        int diffB = _end.getBlue() - _start.getBlue();
+        double elapsedRatio = _elapsed / _duration;
+        return new Color((int)(_start.getRed() + diffR * elapsedRatio),
+                         (int)(_start.getGreen() + diffG * elapsedRatio),
+                         (int)(_start.getBlue() + diffB * elapsedRatio));
+    }
+
+    interface AnimationListener
+    {
+        public abstract void onAnimationFinished();
+    }
+}

Rectangle.java

@@ -86,4 +86,9 @@ class Rectangle implements Drawable {
         _x = x;
         _y = y;
     }
+
+    public void setColor(String c)
+    {
+        _color = c;
+    }
 }

World.java

@@ -8,6 +8,7 @@ class World implements Drawable
     private static final int ACCELERATION = 2;
 
     private final ArrayList<Rectangle> _obstacles;
+    private String _obstacleColor;
     private double _speed;
     private final Random _random;
 
@@ -22,15 +23,28 @@ class World implements Drawable
     public void reset()
     {
         _obstacles.clear();
+        _obstacleColor = "schwarz";
         createObstacle(TurtleWelt.WIDTH);
         _speed = START_SPEED;
     }
 
+    public void setObstacleColor(String c)
+    {
+        for (Drawable d : _obstacles)
+        {
+            if (d instanceof Rectangle)
+            {
+                ((Rectangle)d).setColor(c);
+            }
+        }
+        _obstacleColor = c;
+    }
+
     private void createObstacle(int x)
     {
         int gap = _random.nextInt(TurtleWelt.HEIGHT - 200) + 50;
-        _obstacles.add(new Rectangle(x, 0, 30, gap, "black", false));
+        _obstacles.add(new Rectangle(x, 0, 30, gap, _obstacleColor, false));
-        _obstacles.add(new Rectangle(x, gap + 100, 30, TurtleWelt.HEIGHT, "black", false));
+        _obstacles.add(new Rectangle(x, gap + 100, 30, TurtleWelt.HEIGHT, _obstacleColor, false));
     }
 
     public void update(double elapsed)