ublic void act() 
    {
        if(inTheAir)                //If we're in the air                 
        {                           
            fall();                 //we'll fall
        } else                      //If we're not
        {                           
            if(Greenfoot.isKeyDown("left"))         //If they press the left key
            {
                deltaX = -5;                        //deltaX will move us to left
            } else if(Greenfoot.isKeyDown("right")) //If they press the right key
            {
                deltaX = 5;                         //deltaX will move us right
            } else                                  //If neither key is down
            {                               
                deltaX=0;                           //Don't move at all
            }  

            if(Greenfoot.isKeyDown("up"))           //If we press the up key
            {                                       
                deltaY+=5;                         //Add 15 to deltaY to jump
            }                                       
        }                           
        move();
    } 

public void move()
    {
        int newX = getX() + deltaX;     // Set the new x and y coordinates by adding or subtracting the deltaX

        int newY = getY() - deltaY;     // and deltaY. newX and newY may change if we're on the ground or a platform.
        Actor platformBelow = getOneObjectAtOffset(0, groundHeight+5, Platform.class);  //Look for a platform below us
        Actor platformAbove = getOneObjectAtOffset(0, -groundHeight-5, Platform.class); //Look for a platform above us
        Actor platformToRight = getOneObjectAtOffset(sideWidth+5, 0, Platform.class); //Look for a platform to right of us
        Actor platformToLeft = getOneObjectAtOffset(-(sideWidth+5), 0, Platform.class); //Look for a platform to left of us
        if(platformBelow!=null)         //If we find a platform below us
        {                               
            if(deltaY<0)                //If we are falling
            {                           
                deltaY=0;               //Stop falling
                inTheAir = false;       //Declare we're on the ground
                GreenfootImage platformImage = platformBelow.getImage();                //Get the image of the platform
                int topOfPlatform = platformBelow.getY()-platformImage.getHeight()/2;   //Find the top of platform
                newY = topOfPlatform - groundHeight;                                    //Put our feet at the top of the platform
            }             
        } else if(getY() >= worldHeight - groundHeight) {   //If we hit the ground...
            if(deltaY<0)                                    //and if we're falling...
            {
                deltaY=0;                                   //Stop falling
                inTheAir = false;                           //Declare we're on the ground
                newY = worldHeight - groundHeight;          //Put bottom of actor right on ground
            }
        }  else                          //If there's no platform below
        {                               
            inTheAir = true;            //Then we will be in the air
        }
        if (platformAbove!=null)        //If there's a platform above us
        {                               
            if(deltaY>0)                //If we're going up
            {                           
                deltaY=0;               //Stop going up
                GreenfootImage platformImage = platformAbove.getImage();                //Get the impage of the platform
                int bottomOfPlatform = platformAbove.getY()+platformImage.getHeight()/2;//Find the bottom of the platform
                newY = bottomOfPlatform + groundHeight;                                 //Put the top of our head at the bottom
            }                           
        }
        if(getX()<=sideWidth)
        {
            deltaX=Math.abs(deltaX);
        }
        if(getX()>=worldWidth-sideWidth)
        {
            deltaX=Math.abs(deltaX)*-1;
        }
        if (platformToRight != null)                            //If there's a platform to the right
        {                                                       
            deltaX = Math.abs(deltaX)* -1;                      //Bounce to the left     
        }                                                       
        if (platformToLeft != null)                             //If there is a platform to the right
        {                                                       
            deltaX = Math.abs(deltaX);                          //Bounce to the right
        }