Need advise and help

[iGuest 3]

I want to change something in the script flying planes in dynamic drive libraries

<script language="JavaScript1.2">//Flying planes - by John Ely//Modified from: Autumn leaves script- by Kurt Grigg (kurt.grigg@virgin.net)//Modified by Dynamic Drive for NS6 functionality//visit http://http://www.dynamicdrive.com/ for this script//Pre-load your image below!//CHANGE 5 to the number of images listed belowgrphcs=new Array(5) //PRELOAD the involved images (extend or contract variables according to # of images used)Image0=new Image();Image0.src=grphcs[0]="plane0.gif"Image1=new Image();Image1.src=grphcs[1]="plane1.gif"Image2=new Image();Image2.src=grphcs[2]="plane2.gif"Image3=new Image();Image3.src=grphcs[3]="plane3.gif"Image4=new Image();Image4.src=grphcs[4]="plane4.gif"//SPECIFY number of images to randomly display concurrently from list above. Less the more efficientAmount=3; Ypos=new Array();Xpos=new Array();Speed=new Array();Step=new Array();Cstep=new Array();ns=(document.layers)?1:0;ns6=(document.getElementById&&!document.all)?1:0;ie=document.allif (ns){for (i = 0; i < Amount; i++){var P=Math.floor(Math.random()*grphcs.length);rndPic=grphcs[P];document.write("<LAYER NAME='sn"+i+"' LEFT=0 TOP=0><img src="+rndPic+"></LAYER>");}}else{document.write('<div style="position:absolute;top:0px;left:0px"><div style="position:relative">');for (i = 0; i < Amount; i++){var P=Math.floor(Math.random()*grphcs.length);rndPic=grphcs[P];document.write('<img id="si'+i+'" src="'+rndPic+'" style="position:absolute;top:0px;left:0px">');}document.write('</div></div>');}WinHeight=(ns||ns6)?window.innerHeight-70:window.document.body.clientHeight;WinWidth=(ns||ns6)?window.innerWidth:window.document.body.clientWidth;for (i=0; i < Amount; i++){                                                                 Ypos[i] = Math.round(Math.random()*WinHeight); Xpos[i] = Math.round(Math.random()*WinWidth); Speed[i]= Math.random()*5+1; Cstep[i]=0; Step[i]=Math.random()*0.1+0.05;}function fly(){var WinHeight=(ns||ns6)?window.innerHeight:window.document.body.clientHeight;var WinWidth=(ns||ns6)?window.innerWidth-70:window.document.body.clientWidth;var hscrll=(ns||ns6)?window.pageYOffset:document.body.scrollTop;var wscrll=(ns||ns6)?window.pageXOffset:document.body.scrollLeft;for (i=0; i < Amount; i++){sy = Speed[i]*Math.sin(Cstep[i]);sx = Speed[i]*2;Ypos[i]+=sy;Xpos[i]+=sx; if (Xpos[i] > WinWidth){Ypos[i]=Math.round(Math.random()*WinHeight);Xpos[i]=-60;Speed[i]=Math.random()*5+1;}if (ns){document.layers['sn'+i].left=Xpos[i]+wscrll;document.layers['sn'+i].top=Ypos[i];}else if (ns6){document.getElementById("si"+i).style.left=Xpos[i]+wscrll;document.getElementById("si"+i).style.top=Math.min(WinHeight,Ypos[i]);}else{eval("document.all.si"+i).style.left=Xpos[i]+wscrll;eval("document.all.si"+i).style.top=Ypos[i];} Cstep[i]+=Step[i];}setTimeout('fly()',20);}if (ie||ns||ns6)window.onload=fly//--></script>

the things I want to change is speed of planes and a straight track

Who wants to help me