// Raja Sooriamurthi 11/13/99

import java.awt.*;

public class MoveableBall extends Ball implements Moveable {
    static final int R=3;

    Component cmp;
    double theta;   // direction of motion
    int dx=3, dy=6;

    MoveableBall (Component cmp) {
        super(cmp);
        this.cmp = cmp;
        theta = 2*Math.PI*Math.random();
        dx = (int) (R*Math.cos(theta));
        dy = (int) (R*Math.sin(theta));
    }

    MoveableBall (Component cmp, Point p) {
        super(p);
        this.cmp =  cmp;
        theta = 2*Math.PI*Math.random();
        dx = (int) (R*Math.cos(theta));
        dy = (int) (R*Math.sin(theta));
    }

    public void erase (Graphics g) {
        g.setColor(cmp.getBackground());
        g.fillOval (getX()-radius, getY()-radius, 2*radius, 2*radius);
    }



    public void move() {
        Dimension dim = cmp.getSize();
        if ((getY()<0) || (getY()>dim.height)) theta = -theta;
        if ((getX()<0) || (getX()>dim.width)) 
            theta = Math.PI/2-(theta-Math.PI/2);
        dx = (int) (R*Math.cos(theta));
        dy = (int) (R*Math.sin(theta));
        position.translate(dx, dy);
    }

}