**Dot Clicker**

Here is a dot that has a "is hit" method.  If you want an image instead, take a look at this [[https://mathorama.com/apcs/pmwiki.php?n=Main.ImageMovementApplication|Image Movement Example]]
<code>
import java.awt.Graphics;
import java.awt.Color;
public class Dot
{
    private int x,y,size;
    /**
     * Constructor for objects of class Dot
     */
    public Dot()
    {
        x = 50+(int)(500*Math.random());
        y = 50+(int)(300*Math.random());
        size = 10 +(int)(20*Math.random());
    }

    public Dot(int x,int y,int size)
    {
        this.x = x;
        this.y=y;
        this.size = size;
    }

    public void draw(Graphics g){
        g.setColor(Color.BLACK);
        g.fillOval(x,y,size,size);
    }

    /**
     * returns true if (x0,y0) is inside the dot
     */
    public boolean isHit(int x0, int y0)
    {
        double x2 = x0 - (x+size/2.0);
        double y2 = y0 - (y+size/2.0);
        return x2*x2 + y2*y2 - size*size <0;// Pythagorean theorem
    }
}

</code>

Here is a basic Timer with spawning of dots and expiration of dots

<code>
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.util.ArrayList;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class DotClicker extends JPanel implements MouseListener, ActionListener
{
    public static int WIDTH=800;
    public static int HEIGHT=600;
    private Font titleFont, regularFont;
    private int x,y, hits, misses;
    private Timer spawn, expire;
    private ArrayList<Dot> dots;
    public DotClicker()
    {
        titleFont = new Font("Roman", Font.BOLD, 18);
        regularFont = new Font("Helvetica", Font.PLAIN, 12);
        spawn = new Timer(1000,this);
        expire = new Timer(3000,this);
        dots = new ArrayList<Dot>();
        dots.add(new Dot());
        spawn.start();
        expire.start();
    }

    public static void main(String[] args) {
        DotClicker app= new DotClicker();
        JFrame window = new JFrame("Mouse Listener Application");
        window.setSize(WIDTH, HEIGHT);
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        window.getContentPane().add(app);
        window.getContentPane().addMouseListener(app);
        window.setVisible(true);
    }

    public void paintComponent(Graphics g){
        super.paintComponent(g);
        g.setColor(Color.WHITE);
        g.fillRect(0, 0, getWidth(),getHeight());
        g.setColor(Color.BLUE);
        g.setFont(titleFont);
        g.drawString("Dot Clicker Starter Code", 20, 20);
        g.setColor(Color.BLACK);
        g.setFont(regularFont);
        g.drawString("Hits: "+hits, 20, 40);
        g.drawString("Misses: "+misses, 20, 60);
        //Draw objects
        for(Dot d:dots)
             d.draw(g);		
    }    
    
    /**
     * These are the Methods needed to implement the MouseListener Interface
     */
    public void mouseClicked(MouseEvent e) {}
    public void mousePressed(MouseEvent e) {}
    public void mouseReleased(MouseEvent e) {
        x=e.getX();
        y=e.getY();
        for(int i=dots.size()-1; i >= 0; i--)
        {
            if (dots.get(i).isHit(x,y))
            {
                hits++;
                dots.remove(i);
                repaint();
            }
        }
        repaint();
    }
    public void mouseEntered(MouseEvent e) {}
    public void mouseExited(MouseEvent e) { }
    public void actionPerformed(ActionEvent e) {
	     if (e.getSource()==spawn){
	    	 dots.add( new Dot() );
	     }else if (dots.size()>0){// remove oldest
	         dots.remove(0);
	         misses++;
	     }
	     repaint();
	}
}
</code>