Half of a rectangle.

import java.awt.*;
import java.applet.*;
import java.awt.event.*;
import java.awt.Event.*;
public class col extends Applet implements Runnable
{
    Image Buffer;
    Graphics gBuffer;
    int x, y;
    boolean mouseInside, collide, onderdeel1;
    boolean heen, terug;
    boolean heenschuin, terugschuin;
    Rectangle r1, r2;
    Rectangle bots1,bots2; 

    public void init()
    {
        Buffer=createImage(size().width,size().height);
        gBuffer=Buffer.getGraphics();
        r1=new Rectangle(110,115,10,10);
        r2=new Rectangle(0,0,25,50);
        bots1=new Rectangle(0,0,25,25);
        heen = true;
	terug = false;
        heenschuin = false;
	terugschuin = false;
        onderdeel1 = false;

    }

    public void drawStuff()
    {
        gBuffer.setColor(Color.black);

        gBuffer.fillRect(0,0,size().width,size().height);

        gBuffer.setColor(Color.red);
        gBuffer.fillOval(r1.x, r1.y, r1.width, r1.height);

        gBuffer.setColor(Color.blue);

        gBuffer.fillRect(r2.x, r2.y, r2.width, r2.height);
        gBuffer.setColor(Color.yellow);
        gBuffer.fillRect(r2.x, r2.y, bots1.width, bots1.height);
        gBuffer.setColor(Color.black);

    }

    public boolean mouseEnter(Event evt,int x,int y)
    {
        mouseInside=true;
        repaint();

        return true;
    }

    public boolean mouseExit(Event evt,int x,int y)
    {
        mouseInside=false ;
        repaint();

        return true;
    }

    public boolean mouseMove(Event evt,int x,int y)
    {
        this.x=x;
        this.y=y;
        r2.move(x-r2.width/2, y-r2.height/2);
        drawStuff();

        repaint();
        return true;
    }

    public void update(Graphics g)
    {
        paint(g);
    }

    public void paint(Graphics g)
    {
        drawStuff();
        g.drawImage (Buffer,0,0, this);
    }
public void start(){
      		   Thread tbal = new Thread (this);
                   tbal.start(); 
                   }
public void run (){
      		while (true){ 
		            collide=r2.intersects(r1); 
 		            onderdeel1=bots1.intersects(r1);   
                            if (collide){
                                        if(onderdeel1){
                                                      terug = false;
						      heen  = true;
                                                      collide=false;
                                                      heenschuin = false;
	                                              terugschuin = false;
	                                              onderdeel1 =false;
                                                      }
                                        else{
                                        terug = false;
					heen  = false;
                                        collide=false;
                                        heenschuin = true;
	                                terugschuin = false;
	                                onderdeel1 =false;
                                             }
                                         }
			   else{}
                    
		if(heen && collide==false){
			if ( r1.x >400){
                                      heen = false; terug = true;
			              }
		        else{
                            r1.x=r1.x+2;
                            }
                                          }
		if(heenschuin && collide==false){
			r1.x = r1.x+2;
			r1.y = r1.y+2;
                        }
		if(terug && collide== false){
			if ( r1.x <10){
                                      heen = true; 
                                      terug = false;
			              }
		        else{
                            r1.x=r1.x-2;
                            }
                        }
		if(terugschuin && collide== false){
			r1.x = r1.x-2;
			r1.y = r1.y+2;
                        }	
 repaint();
            			try{
                  		   Thread.sleep (20);
			           }
            			   catch (InterruptedException ex){}
			    repaint();
                            } 
                  }
                                        }