the greenfoot reference pdf doesn't offer much help on this. Here is my current code.
public void act() { { if (Greenfoot.isKeyDown("w")) { move(1); } if (Greenfoot.isKeyDown("s")) { move(-1); } if (Greenfoot.isKeyDown("a")) { turn(-2); move(1); } if (Greenfoot.isKeyDown("d")) { turn(2); move(1); }} if (Greenfoot.isKeyDown("m")) { Bullet bullet = new Bullet(); getWorld().addObject(bullet, getX() + 50, getY()); Greenfoot.setImage(playerfiring.png); }