#!/usr/bin/perl

use CGI; 

$q = new CGI;

$message = $q->param('message'); 
$n1      = $q->param('n1'); 
$n2      = $q->param('n2'); 
$correct = $q->param('correct'); 
$total   = $q->param('total');
$history = $q->param('history'); # state 

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

if ($message) {

  if ($n1 + $n2 == $answer) {
    $correct += 1; 
    $message = "Yes, $n1 + $n2 is INDEED $answer."; 
  } else {
    $message = "No, $n1 + $n2 is NOT $answer."; 
  } 
  $total += 1; 
  $message .= " Score: $correct/$total"; 

  if ($history) { $history .= ";" . $message; }
  else { $history = $message; } 

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

  $question = "What is $n1 + $n2 ? Answer: <input type=text name=answer>"; 
    
} else {
  $message = "Welcome to the game."; 
  $correct = 0; 
  $total = 0; 
  $message .= " Score now $correct out of $total "; 
  $history = ""; 
  $n1 = int(rand(100)) - 50; 
  $n2 = int(rand(100)) - 50; 

  $question = "What is $n1 + $n2 ? Answer: <input type=text name=answer>"; 
}

$hdisplay = "<table cellpadding=2>"; 
@things = split(/;/, $history); 
foreach $thing (@things) {
  ($a, $b) = split(/ Score:/ , $thing); 
  $hdisplay .= "<tr><td bgcolor=lightgrey> $a <td bgcolor=lightgrey> Score: $b "; 
} 
$hdisplay .= "</table>"; 

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

print qq{<form> 
  $message <p> 
  $question <p> 
  <input type="hidden" name="message" value="$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="history" value="$history">

  Press <input type=submit value=Proceed> to move on. <p> 

  $hdisplay 
</form>}; 

print $q->end_html;