solution

src/main/java/lab/App.java

@@ -52,10 +52,13 @@ public class App extends Application {
 	private void drawScene() {
 		//graphic context is used for a painting
 		GraphicsContext gc = canvas.getGraphicsContext2D();
+		World world = new World(canvas.getWidth(), canvas.getHeight());
 		int timeout = 10;
 		while (!Routines.isEndOfThreadRequestedByJavaVM()) {
+			world.draw(gc);
 			Routines.sleep(timeout);
 			double deltaT = timeout / 1000.;
+			world.simulate(deltaT);
 		}
 	}
 	

src/main/java/lab/Bullet.java

+package lab;
+
+import javafx.geometry.Point2D;
+import javafx.scene.canvas.GraphicsContext;
+import javafx.scene.image.Image;
+import javafx.scene.paint.Color;
+
+public class Bullet {
+	private World world;
+	private Point2D startPosition;
+	private Point2D velocity;
+	private double size;
+	private Point2D position;
+	private Image image;
+	public Bullet(World world, Point2D startPosition, Point2D velocity, double size) {
+		super();
+		this.world = world;
+		this.startPosition = startPosition;
+		this.velocity = velocity;
+		this.size = size;
+		this.position = startPosition;
+		image = new Image(Bullet.class.getResourceAsStream("fireball-transparent.gif"));
+		
+	}
+	
+	public void draw(GraphicsContext gc) {
+		gc.save();
+		gc.setFill(Color.BROWN);
+		Point2D p = world.getCanvasPoint(position);
+		//gc.fillOval(p.getX() - size /2, p.getY() - size/2, size, size);
+		gc.drawImage(image, p.getX() - size /2, p.getY() - size/2, size, size);
+		gc.restore();
+	}
+
+	public void simulate(double deltaT) {
+		// TODO Auto-generated method stub
+		position = position.add(velocity.multiply(deltaT));
+	}
+	
+	
+}

src/main/java/lab/Canon.java

+package lab;
+
+import javafx.geometry.Point2D;
+import javafx.scene.canvas.GraphicsContext;
+import javafx.scene.paint.Color;
+import javafx.scene.transform.Affine;
+import javafx.scene.transform.Transform;
+
+public class Canon {
+
+	private Point2D position = new Point2D(10, 30);
+	
+	private int angle = 20;
+	
+	public void draw(GraphicsContext gc) {
+		gc.save();
+		gc.setFill(Color.STEELBLUE);
+		gc.setTransform(new Affine(Transform.rotate(angle, position.getX(), position.getY() + 10)));
+		gc.fillRect(position.getX(), position.getY() + 6, 40, 12);
+		gc.restore();
+	}
+	
+	
+	public void simulate(double deltaT) {
+		angle+= 5;
+	}
+}

src/main/java/lab/World.java

+package lab;
+
+import javafx.geometry.Point2D;
+import javafx.scene.canvas.GraphicsContext;
+import javafx.scene.paint.Color;
+
+public class World {
+	
+	private double width;
+	
+	private double height;
+
+	private Bullet bullet;
+
+	private Canon canon;
+
+	public World(double width, double height) {
+		this.width = width;
+		this.height = height;
+		this.bullet = new Bullet(this, new Point2D(10, 10), new Point2D(10, 30), 40);
+		this.canon = new Canon();
+	}
+	
+	public Point2D getCanvasPoint(Point2D in) {
+		Point2D result = new Point2D(in.getX(), height - in.getY());
+		return result;
+	}
+	
+	public void draw(GraphicsContext gc) {
+		gc.save();
+		gc.setFill(Color.LIGHTGREY);
+		gc.fillRect(0, 0, width, height);
+		gc.restore();
+		bullet.draw(gc);
+		canon.draw(gc);
+	}
+	
+	public void simulate(double deltaT) {
+		this.bullet.simulate(deltaT);
+		this.canon.simulate(deltaT);
+	}
+}