Hoger/Lager Game met layout!

[code]<?php
ini_set('display_errors', 1); // 0 = uit, 1 = aan
error_reporting(E_ALL);

session_start();
$nummer1 = (isset($_SESSION['nummer1'])) ? $_SESSION['nummer1'] : rand(0, 100);

if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    $nummer2 = rand(0, 100);
    if (isset($_POST['hoger'])) {
        if ($nummer1 > $nummer2) {
            echo '<center>Het getal was <b>'.$nummer1.'</b>, het nieuwe getal was <b>'.$nummer2.'</b>.<br>Het nieuwe getal was lager, dus <b><p style="color: red">je verliest!</p></b></center>';
        } else {
            echo '<center>Het getal was <b>'.$nummer1.'</b>, het nieuwe getal was <b>'.$nummer2.'</b>.<br>Het nieuwe getal was hoger, dus <b><p style="color: green">je wint!</p></b></center>';
        }
    } else {
        if ($nummer1 < $nummer2) {
            echo '<center>Het getal was <b>'.$nummer1.'</b>, het nieuwe getal was <b>'.$nummer2.'</b>.<br>Het nieuwe getal was hoger, dus <b><p style="color: red">je verliest!</p></b></center>';
        } else {
            echo '<center>Het getal was <b>'.$nummer1.'</b>, het nieuwe getal was <b>'.$nummer2.'</b>.<br>Het nieuwe getal was lager, dus <b><p style="color: green">je wint!</p></b></center>';
        }
    }
}
?>
<center>

Het getal is <b>

<?php
$nummer1 = rand(0, 100);
echo $nummer1;
$_SESSION['nummer1'] = $nummer1;
?>

</b><br>Is het volgende getal...<br><br>
<form method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>">
<input type="submit" name="hoger" value="Hoger"> of <input type="submit" name="lager" value="Lager">?
</form> 

<style>

html, body {
	margin: 0;
	padding: 0;
	background-color: #f2f2f2;
	height: 100%;
	line-height: 1.4em;
}

html, body, th, td, input, textarea, select {
	font: 11px Verdana, Arial, Helvetica, sans-serif;
	color: #000;
}

a, a:link, a:visited, a:active {
	color: #17407e;
	text-decoration: none;
}

a:hover {
	text-decoration: underline;
}

input, textarea {
	background: #fff;
	border: 1px #ddd solid;
	border-bottom: 2px #ddd solid;
	padding: 1px;
}

button {
	font: 700 11px Verdana, Arial, Helvetica, sans-serif;
}

img {
	border: 0;
}

table {
	width: 100%;
}

th {
	font-weight: 700;
}

h1 {
	font: 700 16px Verdana, Arial, Helvetica, sans-serif;
}

h2 {
	font: 700 15px Verdana, Arial, Helvetica, sans-serif;
}

h3 {
	font: 700 14px Verdana, Arial, Helvetica, sans-serif;
}
</style></center>[/code]