OLPCities/Using Transit

The sprite whose name is "Transit" is a green paralelogram that is used to link a Lot to the next Lot at East, West, North or South. Look the image (you can download and use it):

Like we saw at the previous lesson, when the avatar goes to a Lot he needs to know what is it's entry position and frame. We define this using a cookie whose name can be "entryt" or anyone you like (always the same, of course).

Look the figure. If the avatar is colliding against a TransitW you need to make: entryt = "E" and, at the new Lot, we will have the test:

...
if(entryt.value=="E"){	  
  av.moveTo( 550,165);	 
  av.setFrame(0);
...

Frame 0 (zero) means tha avatar looking to west.

Sometimes the Transit only appears only when the kid do some activity at the Lot with success.

At our exercice we have three Lots. You will go to the central and can go West or East. Take a look at the code of the central Lot:

<html>
<head>
<script language="Javascript" 

src="http://www.dmu.com/olpc/gamelib_core.js"></script> 
<script language="Javascript"  

src="http://www.dmu.com/olpc/gamelib_sprites.js"></script>
<script language="Javascript" 

src="http://www.dmu.com/olpc/gamelib_keyboard.js"></script>
<script language="Javascript">

 
 
 
 function init(){

  Sp_linuxcompatible=true;

  Gl_preloader("floorW05N07.gif"); 
  Gl_preloader("transit.gif"); 
  Gl_preloader("avat1.gif"); 

  entryt = new Gl_cookie("entt");

   upkey=Kb_trapkey("UP");				 
   downkey=Kb_trapkey("DOWN");			  
   rightkey=Kb_trapkey("RIGHT");	
   leftkey=Kb_trapkey("LEFT");
 
   av=new Sp_Sprite();	 
   av.setImage("avat1.gif",32,32,4,2);  
   av.setXlimits(5,610);
   av.setYlimits(5,385);
   if(entryt.value=="E"){	  
    av.moveTo( 550,165);	 
    av.setFrame(0);
    entryt.setvalue("G");
    }
    else if(entryt.value=="W"){	 
     av.moveTo(30,175);	 
     av.setFrame(1);
     entryt.setvalue("G");
   }
   else{
    av.moveTo( 300,170);	 
    av.setFrame(3);
   }			 
   av.setFrameByDirection(90,90,1,180,180,3,270,270,0,0,0,2);
   av.setAnimation(0);
   av.setZ(10);
   av.collides=true;
   av.useHitEvents(true);
   av.setAnimationSpeed(3);
   av.switchOn();

  floor=new Sp_Sprite();			 
  floor.setImage("floorW05N07.gif",614,390,1,1); 
  floor.setXlimits( 0,616);	 
  floor.setYlimits( 0,390);
  floor.setFrame(0);	 
  floor.moveTo(0 , 0 );				 
  floor.setZ(5);  
  floor.switchOn();				 

  transitW=new Sp_Sprite();			 
  transitW.setImage("transit.gif",20,20,1,1); 
  transitW.setXlimits( 0,614);	 
  transitW.setYlimits( 0,390);
  transitW.setFrame(0);	 
  transitW.moveTo(5 , 180 );		 
  transitW.setZ(12);  
  transitW.makeHard();
  transitW.switchOn();
  

  transitE=new Sp_Sprite();		 
  transitE.setImage("transit.gif",20,20,1,1); 
  transitE.setXlimits( 0,614);	 
  transitE.setYlimits( 0,390);
  transitE.setFrame(0);	 
  transitE.moveTo(590 , 180 );		 
  transitE.setZ(12);  
  transitE.makeHard();
  transitE.switchOn();	 


  Gl_hook("timestep()"); 
  Gl_start();	
 } 

 function timestep(){
    av.setSpeed(0); 
    av.setAnimationRepeat(0);
   if(rightkey.pressed){
     av.setDir(1,0);
     av.setAnimationRepeat(-1);
     av.setSpeed(2);
   }
   else if(leftkey.pressed){
    av.setDir(-1,0);
    av.setAnimationRepeat(-1);
    av.setSpeed(2);
   }
   else if(downkey.pressed){
    av.setDir(0,1);
    av.setAnimationRepeat(-1);
    av.setSpeed(2);
   }
   else if(upkey.pressed){
    av.setDir(0,-1);
    av.setAnimationRepeat(-1);
    av.setSpeed(2);
   }

   if(av.hasHit(transitE)){
    entryt.setvalue("W");   
    window.location="tut5e.html";
   } 
   if(av.hasHit(transitW)){
    entryt.setvalue("E");   
    window.location="tut5w.html";
   } 
 }//timestep

</script>
</head>

<title>TUTCITY  </title>
<body  bgcolor="black"  onload="init()" >
</html>

OLPCities/Using Transit

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