#!/usr/bin/perl

use CGI; 

$q = new CGI; 

print $q->header, $q->start_html; 

$message = $q->param('message'); 
$n1      = $q->param('n1'); 
$n2      = $q->param('n2'); 
$correct = $q->param('correct'); 
$total   = $q->param('total'); 
$table   = $q->param('table'); # all of the above are state

$answer = $q->param('answer'); # input 

if ($message) {

  if ($answer == $n1 + $n2) {
    $message = "$n1 + $n2 is INDEED equal to $answer "; 
    $correct += 1; 
  } else { 
    $message = "$n1 + $n2 is NOT equal to $answer "; 
  }   
  $total += 1; 
  $message .= "(score now $correct/$total) "; 

  # store in the table 
  # table has the format: sdjkfgsd:sfgesdf:agdsdjhfd:kjsdagfsd  
  if ($table) { $table .= ":" . $message; } 
  else { $table = $message; } 

  $n1 = int(rand(100)) - 50; 
  $n2 = int(rand(100)) - 50; 
  # $question is an output variable not part of the state 
  $question = "What is $n1 + $n2? Answer: <input type=text name=answer> "; 

} else {

  # initialize state 
  $correct = 0; 
  $total = 0; 
  $message = "Welcome the game starts at $correct out of $total "; 

  $table = "";

  $n1 = int(rand(100)) - 50; 
  $n2 = int(rand(100)) - 50; 

  # $question is an output variable not part of the state 
  $question = "What is $n1 + $n2? Answer: <input type=text name=answer> "; 

} 

print qq{<form>
  $message <p> 
  $question <p> 
  Press <input type="submit" value="Proceed"> to move on. 
  <input type=hidden name="message" value="$message">
  <input type=hidden name="n1"      value="$n1">
  <input type=hidden name="n2"      value="$n2">
  <input type=hidden name="correct" value="$correct">
  <input type=hidden name="total"   value="$total">
  <input type=hidden name="table"   value="$table">
</form>};

print "<table border>"; 
@lines = split(/:/, $table); 
foreach $line (@lines) {
  ($a, $b) = split(/ \(/, $line);
  print "<tr><td> $a <td> ($b"; 
}
print "</table>"; 
print $q->end_html;