<SCRIPT LANGUAGE="JavaScript">
<!--// Copyright (c) 1996 Tomer Shiran. All rights reserved.
// Permission given to use this script provided that the copyright
// notice remains as is. Additional scripts and information are 
// available at http://www.oocities.org/SiliconValley/9000/
// assign initial values to global variables
var total = 0
var play = false
// react to a click in a checkbox (element == clicked checkbox object)

function display(element) { 
 // assign instance of Date object representing current time 
  var now = new Date() 
 // if the game has not started yet 
  if (!play) {  
 // game starts now  
  play = true  
 // milliseconds since 1970 for time at beginning   
  startTime = now.getTime() 
 } 
 // if more than 20 seconds have passed since startTime was last set 
  if (now.getTime() - startTime > 20000) {  
   // reject modification (make "read-only")  
    element.checked = !element.checked  
   // terminate function  
   return 
  } 
 // if the clicked checkbox is now checked 
  if (element.checked)  
   // increment total  
    total++
  else  
   // decrement total  
    total-- 
   // display total in text object 
    element.form.num.value = total
}

function restart(form) { 
 // set global variables back to initial values 
  total = 0 
  play = false 
 // uncheck all 100 checkboxes 
  for (var i = 1; i <= 100; ++i) {  
   // uncheck current checkbox  
    form.elements[i].checked = false 
  }
}
// -->
</SCRIPT>
<SCRIPT LANGUAGE="JavaScript">
<!--// immediate script (executed before the other script because it is deferred)
 document.write("<FORM><CENTER>")
 document.write('<INPUT TYPE="text" VALUE="0" NAME="num" SIZE=10 onFocus="this.blur()"><BR>')
 document.write("<HR SIZE=1 WIDTH=40%>")
// use loop to create a 10 x 10 square of checkboxes
 for (var i = 0; i < 10; ++i) { 
  for (var j = 0; j < 10; ++j) {  
   // write checkbox with "display(this)" as event handler script  
    document.write('<INPUT TYPE="checkbox" onClick="display(this)">') 
  } 
  document.write("<BR>")
 }
 document.write("<HR SIZE=1 WIDTH=40%>")
 // create button to call restart function to restart game
  document.write('<INPUT TYPE="button" VALUE="restart" onClick="restart(this.form)">')
  document.write("</CENTER></FORM>")
// -->
</SCRIPT>