1. create an empty welcome_text.php
2. insert the following code in it:
<?php
$welcomeText = 'Your default text here';
$frontPageText = 'Text for the front page'; // leave the string empty ('') to use the default one.
$gamePageText = 'Text for game pages'; // leave the string empty ('') to use the default one.
$categoryText = array(
1 => 'Text for the category with ID = 1',
4 => 'Text for another category'
// and so on.
// category IDs can be found on the cat. management page inside admin cp
);
$sScript = substr(strrchr($_SERVER['PHP_SELF'], "/"), 1);
if( $sScript == 'cat.php' )
{
if( !empty($categoryText[$nCategory]) )
$welcomeText = $categoryText[$nCategory];
}
elseif( $sScript == "index.php" )
{
if( !empty($frontPageText) )
$welcomeText = $frontPageText;
}
elseif( $sScript == "game.php" )
{
if( !empty($gamePageText) )
$welcomeText = $gamePageText;
}
$tpl->assign( "WELCOMETEXT", $welcomeText );
?>
3. upload the file to /content/blocks/ folder
4. in your admin cp edit settings for the "Welcome" block - switch its type to "PHP Script"
That's it.
Warning: the method is untested, so please post your results/questions here, I'll try to help.