import greenfoot.*;  // (World, Actor, GreenfootImage, and Greenfoot)  /**  * A little penguin that wants to get to the other side.  */ public class Pengu extends Mover {     private static final int jumpStrength = 16;          public void act()      {         checkKeys();                 checkFall();     }          private void checkKeys()     {         if (Greenfoot.isKeyDown("left") )         {             setImage("pengu-left.png");             moveLeft();         }         if (Greenfoot.isKeyDown("right") )         {             setImage("pengu-right.png");             moveRight();         }         if (Greenfoot.isKeyDown("space") )         {             if (onGround())                 jump();         }     }              private void jump()     {         setVSpeed(-jumpStrength);         fall();     }          private void checkFall()     {         if (onGround()) {             setVSpeed(0);         }         else {             fall();         }     }   }