Solution

src/main/java/lab/BulletAnimated.java

 package lab;
 
 import javafx.geometry.Point2D;
+import javafx.geometry.Rectangle2D;
 import javafx.scene.canvas.GraphicsContext;
 import javafx.scene.image.Image;
 
@@ -82,4 +83,7 @@ public class BulletAnimated {
 		accelerate = true;
 	}
 	
+	public Rectangle2D getBoundingBox() {
+		return new Rectangle2D(position.getX(), position.getY(), size, size);
+	}
 }

src/main/java/lab/Constants.java

@@ -13,7 +13,11 @@ public final class Constants {
 	
 	public static final Image DRAGON_IMAGE;
 	
+	public static final Image DESERT_IMAGE;
+	
+	
 	static{ 
 		DRAGON_IMAGE = new Image(Constants.class.getResourceAsStream("dragon.gif"));
+		DESERT_IMAGE = new Image(Constants.class.getResourceAsStream("desert-1654439__340.jpeg"));
 	}
 }

src/main/java/lab/Dragon.java

+package lab;
+
+import javafx.geometry.Point2D;
+import javafx.geometry.Rectangle2D;
+import javafx.scene.canvas.GraphicsContext;
+import javafx.scene.image.Image;
+
+public class Dragon {
+
+	private static final int DRAGON_SIZE = 50;
+	private Point2D pos;
+	private Point2D vel;
+	private Image image;
+	private World world;
+	public Dragon(World w, Point2D pos, Point2D vel) {
+		this.pos = pos;
+		this.vel = vel;
+		this.image = Constants.DRAGON_IMAGE;
+		this.world = w;
+	}
+	
+	public void draw(GraphicsContext gc) {
+		Point2D p = world.getCanvasPoint(pos);
+		gc.drawImage(image, p.getX(), p.getY(), DRAGON_SIZE, DRAGON_SIZE);
+	}
+
+	public void simulate(double deltaT) {
+		pos = pos.add(vel.multiply(deltaT));
+		pos = new Point2D((pos.getX() +world.getWidth())% world.getWidth(), (pos.getY()+world.getHeight()) % world.getHeight());
+	}
+	
+	public Rectangle2D getBoundingBox() {
+		return new Rectangle2D(pos.getX(), pos.getY(), DRAGON_SIZE, DRAGON_SIZE);
+	}
+
+	public void hit() {
+		vel = vel.multiply(-1);
+	}
+}

src/main/java/lab/World.java

 package lab;
 
+import java.util.Random;
+
 import javafx.geometry.Point2D;
 import javafx.scene.canvas.Canvas;
 import javafx.scene.canvas.GraphicsContext;
@@ -9,13 +11,24 @@ public class World {
 	private double height;
 	private BulletAnimated bulletAnimatted;
 	private Cannon cannon;
-
+	private Dragon []dragons;
+	
 	public World(double width, double height) {
 		super();
 		this.width = width;
 		this.height = height;
 		cannon = new Cannon(this, new Point2D(50, 50), new Point2D(100, 20));
 		bulletAnimatted = new BulletAnimated(this, cannon, new Point2D(30, 60), new Point2D(0, 0), 40);
+		
+		Random rnd = new Random();
+		dragons = new Dragon[5];
+		for (int i = 0; i < dragons.length; i++) {
+			int x = rnd.nextInt((int) width);
+			int y = rnd.nextInt((int) height);
+			int v_x = rnd.nextInt(10) - 5;
+			int v_y = rnd.nextInt(10) - 5;
+			dragons[i] = new Dragon(this, new Point2D(x, y), new Point2D(v_x*10, v_y*10));
+		}
 	}
 
 	public Point2D getCanvasPoint(Point2D worldPoint) {
@@ -24,14 +37,26 @@ public class World {
 
 	public void draw(Canvas canvas) {
 		GraphicsContext gc = canvas.getGraphicsContext2D();
-		gc.clearRect(0, 0, canvas.getWidth(), canvas.getHeight());
+		gc.drawImage(Constants.DESERT_IMAGE, 0, 0, width, height);
 		cannon.draw(gc);
 		bulletAnimatted.draw(gc);
+		for (Dragon d: dragons) {
+			d.draw(gc);
+		}
 	}
 
 	public void simulate(int timeDelta) {
 		bulletAnimatted.simulate(timeDelta);
 		cannon.simulate(timeDelta);
+		for (Dragon d: dragons) {
+			d.simulate(timeDelta/1000.0);
+		}
+		for (Dragon d: dragons) {
+			if (d.getBoundingBox().intersects(bulletAnimatted.getBoundingBox())) {
+				d.hit();
+				bulletAnimatted.reload();
+			}
+		}
 	}
 
 	public double getWidth() {