solution

src/main/java/lab/App.java

@@ -5,6 +5,7 @@ import javafx.application.Application;
 import javafx.scene.Group;
 import javafx.scene.Scene;
 import javafx.scene.canvas.Canvas;
+import javafx.scene.paint.Color;
 import javafx.stage.Stage;
 import javafx.stage.WindowEvent;
 
@@ -18,7 +19,6 @@ public class App extends Application {
 		launch(args);
 	}
 	
-	private Canvas canvas;
 	private AnimationTimer timer;
 	
 	@Override
@@ -26,9 +26,10 @@ public class App extends Application {
 		try {
 			//Construct a main window with a canvas.  
 			Group root = new Group();
-			canvas = new Canvas(800, 400);
+			Canvas canvas = new Canvas(800, 400);
 			root.getChildren().add(canvas);
 			Scene scene = new Scene(root, 800, 400);
+			scene.setFill(Color.BLANCHEDALMOND);
 			scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
 			primaryStage.setScene(scene);
 			primaryStage.resizableProperty().set(false);

src/main/java/lab/Bullet.java

+package lab;
+
+import javafx.geometry.Point2D;
+import javafx.scene.canvas.GraphicsContext;
+import javafx.scene.paint.Color;
+
+public class Bullet {
+
+	private final World world;
+	private Point2D position;
+	private Point2D velocity;
+	private final double size;
+	
+	public Bullet(World world, Point2D position, Point2D velocity, double size) {
+		this.world = world;
+		this.position = position;
+		this.velocity = velocity;
+		this.size = size;
+	}
+
+	public void simulate(double deltaT) {
+		position = position.add(velocity.multiply(deltaT));
+		position = new Point2D((position.getX() + world.getWidth())  % world.getWidth(), (position.getY() + world.getHeight()) % world.getHeight());
+	}
+
+	public void draw(GraphicsContext gc) {
+		gc.setFill(Color.RED);
+		Point2D p = world.transform2Canvas(position);
+		gc.fillOval(p.getX(),  p.getY(), size, size);
+	}
+
+	protected World getWorld() {
+		return world;
+	}
+
+	protected Point2D getPosition() {
+		return position;
+	}
+
+	protected double getSize() {
+		return size;
+	}
+	
+	
+	
+	//simulate
+	
+	//draw
+	
+}

src/main/java/lab/BulletAnimated.java

+package lab;
+
+import javafx.geometry.Point2D;
+import javafx.scene.canvas.GraphicsContext;
+import javafx.scene.image.Image;
+
+public class BulletAnimated extends Bullet{
+
+	
+	public BulletAnimated(World world, Point2D position, Point2D velocity, double size) {
+		super(world, position, velocity, size);
+	}
+
+	private Image image = new Image(getClass().getResourceAsStream("fireball-transparent.gif"));
+	//gc.drawImage(image, width, height)
+	
+	@Override
+	public void draw(GraphicsContext gc) {
+		Point2D p = getWorld().transform2Canvas(getPosition());
+		gc.drawImage(image,p.getX(), p.getY(), getSize(), getSize());
+	}
+	
+}

src/main/java/lab/Cannon.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 Cannon {
+
+	private World world;
+	private final Point2D position;
+	private double angle;
+	private int speed = 10;
+
+	public Cannon(World world, Point2D position, double angle) {
+		this.world = world;
+		this.position = position;
+		this.angle = angle;
+	}
+
+	public void draw(GraphicsContext gc) {
+		gc.save();
+		gc.setFill(Color.LIGHTSTEELBLUE);
+		Point2D p = world.transform2Canvas(position);
+		gc.setTransform(new Affine(Transform.rotate(-angle, p.getX(), p.getY())));
+		gc.fillRect(p.getX(), p.getY(), 100, 20);
+		gc.restore();
+	}
+
+	public void simulate(double deltaT) {
+		angle = angle + speed*deltaT;
+		if (angle > 90) {
+			angle = 180 - angle;
+			speed  *= -1;
+		} else if (angle < 0){
+			angle = -angle;
+			speed  *= -1;
+		}
+	}
+	
+	
+	
+}

src/main/java/lab/DrawingThread.java

@@ -8,9 +8,11 @@ public class DrawingThread extends AnimationTimer {
 
 	private final GraphicsContext gc;
 	private long lastTime;
-
+	private final World world;
+	
 	public DrawingThread(Canvas canvas) {
 		this.gc = canvas.getGraphicsContext2D();
+		this.world = new World(canvas.getWidth(), canvas.getHeight());
 	}
 
 	/**
@@ -21,8 +23,10 @@ public class DrawingThread extends AnimationTimer {
 		if (lastTime > 0) {
 			double deltaT = (now - lastTime) / 1e9;
 			// call simulate on world
+			world.simulate(deltaT);
 		}
 		//call draw on world
+		world.draw(gc);
 		lastTime= now;
 
 	}

src/main/java/lab/World.java

+package lab;
+
+import javafx.geometry.Point2D;
+import javafx.scene.canvas.GraphicsContext;
+
+public class World {
+	private final double width;
+	
+	private final double height;
+
+	private final Bullet bullet;
+
+	private final Cannon cannon;
+	
+	public World(double width, double height) {
+		this.width = width;
+		this.height = height;
+		this.bullet = new BulletAnimated(this, new Point2D(50, 50), new Point2D(100, 100), 30);
+		this.cannon = new Cannon(this, new Point2D(50, 50), 45);
+	}
+	
+	public void simulate(double deltaT) {
+		this.bullet.simulate(deltaT);
+		this.cannon.simulate(deltaT);
+	}
+
+	public void draw(GraphicsContext gc) {
+		gc.clearRect(0, 0, width, height);
+		this.bullet.draw(gc);
+		this.cannon.draw(gc);
+	}
+	
+	public Point2D transform2Canvas(Point2D p) {
+		return new Point2D(p.getX(), height - p.getY());
+	}
+
+	public double getWidth() {
+		return width;
+	}
+
+	public double getHeight() {
+		return height;
+	}
+	
+	
+}