Editing CleverCritters

<edcode> 
var worldWidth=640;
var worldHeight=480;

var critterBrian = {x:320,y:240,dx:1,dy:0.5};
var critterFrank = {x:120,y:140,dx:1,dy:0.5};
var critterSally = {x:120,y:340,dx:1,dy:0.5};
var critterGerald = {x:420,y:140,dx:1,dy:0.5};
var critterLucy = {x:420,y:340,dx:1,dy:0.5};

var allCritters = [critterBrian,critterFrank,critterSally,critterGerald,critterLucy];

function moveCritter(critter) {
  critter.x+=critter.dx;
  critter.y+=critter.dy;

  if (critter.x<0) critter.x+=worldWidth;
  if (critter.x>worldWidth) critter.x-=worldWidth;
  if (critter.y<0) critter.y+=worldHeight;
  if (critter.y>worldHeight) critter.y-=worldHeight;


  var tweakX = Math.random()-0.5;
  var tweakY = Math.random()-0.5;
  //tweakX and tweakY now have random values between -0.5 and +0.5

  critter.dx+=tweakX;
  critter.dy+=tweakY;
  
  critter.dx*=0.99;
  critter.dy*=0.99;
}

function drawCritter(critter) {
  fillCircle(critter.x,critter.y,5);
}

function move() {
  allCritters.each(moveCritter);
}

function draw() {
  clear();
  allCritters.each(drawCritter);
}

run(move,draw);
</edcode>