i got nothing. Totally lost.
import greenfoot.*;
public class Arrow extends Actor
{
private int xSpeed, ySpeed; // movement fields
public Arrow()
{
xSpeed = 20; // horizontal speed
ySpeed = -15; // initial vertical speed
}
public void act()
{
setLocation(getX()+xSpeed, getY()+ySpeed++); // move and apply gravity
setRotation((int)(Math.atan2(ySpeed, xSpeed)*180/Math.PI)); // adjust rotation
if (isAtEdge()) getWorld().removeObject(this); // remove at edge
}
}