<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.geocities.com/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>
<!-- END OF SCRIPT -->