Building Browsergames » perl http://buildingbrowsergames.com Ever wanted to build a browsergame? Mon, 29 Mar 2010 14:00:39 +0000 http://wordpress.org/?v=2.8.5 en hourly 1 Implementing Multiple Areas (Perl) http://buildingbrowsergames.com/2009/01/19/implementing-multiple-areas-perl/ http://buildingbrowsergames.com/2009/01/19/implementing-multiple-areas-perl/#comments Mon, 19 Jan 2009 14:00:58 +0000 Luke http://buildingbrowsergames.com/?p=689 Now that our database is prepared for multiple areas, we are going to build multiple areas into our exploration/combat system.

To start off, check out version 47 of our code from the Google Code Project:

svn checkout http://building-browsergames-tutorial.googlecode.com/svn/trunk/php/pbbg tutorial -r 47

With a fresh checkout of the code, we can get started. The first thing we will do is copy the code from forest.cgi over to explore.cgi, which is where we will now be storing our exploration code. Once that’s done, we will need to change the way that our script retrieves the current monster for a player to fight:

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my $area_id = $query->url_param('area');
$sth = $dbh->prepare("SELECT monster FROM area_monsters WHERE area = ? ORDER BY RAND() LIMIT 1");
$sth->execute($area_id);
my $monster_id;
$sth->bind_columns(\$monster_id);
$sth->fetch;
$sth = $dbh->prepare("SELECT name FROM monsters WHERE id = ?");
$sth->execute($monster_id);
$sth->bind_columns(\$parameters{monster});
$sth->fetch;

Because we will be intermingling arguments passed through both GET and POST for our code, we have to use the url_param method – we will also need to make a slight change to how we determine whether we’re being POST’d to or not:

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if($query->request_method() eq 'POST') {

With our code changes made, we need to put areas and monsters in areas into our database for our code to retrieve:

INSERT INTO areas(name) VALUES ('Forest');
INSERT INTO areas(name) VALUES ('Woods');
INSERT INTO area_monsters(area,monster) VALUES (1,1);
INSERT INTO area_monsters(area,monster) VALUES (1,2);
INSERT INTO area_monsters(area,monster) VALUES (2,3);

Once the data is inserted, our changes are (mostly) complete. Try visiting explore.cgi?area=1, and refreshing a few times – you should only ever see monsters appearing that belong in the area with the ID of 1.

While you are testing that, you may have noticed that the title tag for our page still says ‘The Forest’ – we should probably modify our code to also retrieve the name of the area we’re visiting:

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my $area_id = $arguments{'area'};
$sth = $dbh->prepare("SELECT name FROM areas WHERE id = ?");
$sth->execute($area_id);
$sth->bind_columns(\$parameters{area_name});
$sth->fetch;
 
my $template = HTML::Template->new(
		filename	=>	'explore.tmpl',

With that code added, it’s easy enough to tweak our template(renamed from forest.tmpl to explore.tmpl) to display the current area in it’s <title> tag, in addition to changing where our combat form POSTs to:

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    	<title>The <!--tmpl_var name='area_name'--></title>
    </head>
    <body>
    	<tmpl_unless name='combat'>
    		<p>You've encountered a <!--tmpl_var name='monster'-->!</p>
    		<form action='explore.cgi?area=<!--tmpl_var name='area'-->' method='post'>
    			<input type='submit' name='action' value='Attack' /> or 
    			<input type='submit' name='action' value='Run Away' />
    			<input type='hidden' name='monster' value='<!--tmpl_var name='monster'-->' />
    		</form>
    	<tmpl_else>
    		<ul>
    		<tmpl_loop name='combat'>
    			<li><strong><!--tmpl_var name='attacker'--></strong> attacks <!--tmpl_var name='defender'--> for <!--tmpl_var name='damage'--> damage!</li>
    		</tmpl_loop>
    		</ul>
    		<tmpl_if name='won'>
    			<p>You killed <strong><!--tmpl_var name='monster'--></strong>! You gained <strong><!--tmpl_var name='gold'--></strong> gold, and <strong><!--tmpl_var name='exp'--></strong> experience.</p>
    			<tmpl_if name='level_up'>
        			<p><strong>You gained a level!</strong></p>
    			</tmpl_if>
    			<p>You found a <strong><!--tmpl_var name='item'--></strong>!</p>
    			<p><a href='explore.cgi?area=<!--tmpl_var name='area'-->'>Explore Again</a></p>

With our template changes finished, we’re done! Your game can now support multiple different areas that players can encounter enemies in – all you have to do is link them to explore.cgi?area=<area_id>, where <area_id> is an ID for an area in the database. Here’s what our new code looks like:

explore.cgi:

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#!/usr/bin/perl -w
 
use strict;
use CGI qw(:cgi);
use CGI::Carp qw(warningsToBrowser fatalsToBrowser);
use Data::Dumper;
use HTML::Template;
use DBI;
use config;
use weaponstats;
 
my $query = new CGI;
my %arguments = $query->Vars;
 
my $dbh = DBI->connect("DBI:mysql:$config{dbName}:$config{dbHost}",$config{dbUser},$config{dbPass},{RaiseError => 1});
my $sth;
my %parameters;
 
if($query->request_method() eq 'POST') {
	if($arguments{action} eq 'Attack') {
		# fighting the monster	
		use stats;
		use monsterstats;
		my $cookie = $query->cookie('username+password'); 
		my ($username) = split(/\+/,$cookie);
		$sth = $dbh->prepare("SELECT id FROM users WHERE UPPER(username) = UPPER(?)");
		$sth->execute($username);
		my $userID;
		$sth->bind_columns(\$userID);
		$sth->fetch;
		my %player = (
			name		=>	$username,
			attack		=>	stats::getStat('atk',$userID),
			defence		=>	stats::getStat('def',$userID),
			curhp		=>	stats::getStat('curhp',$userID)
		);
		my $phand = stats::getStat('phand',$userID);
		$player{attack} += weaponstats::getWeaponStat('atk',$phand);
		use armorstats;
		my @armor = qw(atorso ahead alegs aright aleft);
		foreach my $key(@armor) {
			my $id = stats::getStat($key,$userID);
			my $defence = armorstats::getArmorStat('defence',$id);
			$player{defence} += $defence;
		}		
		$sth = $dbh->prepare("SELECT id FROM monsters WHERE name = ?");
		$sth->execute($arguments{monster});
		my $monsterID;
		$sth->bind_columns(\$monsterID);
		$sth->fetch;
		my %monster = (
			name		=>	$arguments{monster},
			attack		=>	monsterstats::getMonsterStat('atk',$monsterID),
			defence		=>	monsterstats::getMonsterStat('def',$monsterID),
			curhp		=>	monsterstats::getMonsterStat('maxhp',$monsterID)
		);
		my @combat;
		my $turns = 0;
		my ($attacker,$defender);
		while($player{curhp} > 0 && $monster{curhp} > 0) {
			my %attack;
			if($turns % 2 != 0) {
				$attacker = \%monster;
				$defender = \%player;
			} else {
				$attacker = \%player;
				$defender = \%monster;
			}
			my $damage = 0;
			if($attacker->{attack} > $defender->{defence}) {
				$damage = $attacker->{attack} - $defender->{defence};	
			}
			my %attack = (
				attacker => $attacker->{name},
				defender => $defender->{name},
				damage => $damage
			);
			$defender->{curhp} -= $damage;
			push @combat, \%attack;
			$turns++;
		}
		stats::setStat('curhp',$userID,$player{curhp});
		if($player{curhp} > 0) {
			# player won
			stats::setStat('gc',$userID,stats::getStat('gc',$userID) + monsterstats::getMonsterStat('gc',$monsterID));
			$parameters{won} = 1;
			$parameters{gold} = monsterstats::getMonsterStat('gc',$monsterID);
			my $rand = int(rand(99))+1;
			$sth = $dbh->prepare("SELECT item_id FROM monster_items WHERE monster_id = ? AND rarity >= ? ORDER BY RAND() LIMIT 1");
			$sth->execute($monsterID,$rand);
			my $itemID;
			$sth->bind_columns(\$itemID);
			$sth->fetch;
			$sth = $dbh->prepare("SELECT count(id) FROM user_items WHERE user_id = ? AND item_id = ?");
			$sth->execute($userID,$itemID);
			my $count;
			$sth->bind_columns(\$count);
			$sth->fetch;
			if($count > 0) {
				# already has one of the item
				$sth = $dbh->prepare("UPDATE user_items SET quantity = quantity + 1 WHERE user_id = ? AND item_id = ?");
			} else {
				# has none of the item - new row
				$sth = $dbh->prepare("INSERT INTO user_items(quantity,user_id,item_id) VALUES (1,?,?)");
			}
			$sth->execute($userID,$itemID);
			$sth = $dbh->prepare("SELECT name FROM items WHERE id = ?");
			$sth->execute($itemID);
			$sth->bind_columns(\$parameters{item});
			$sth->fetch;
 
            my $monster_exp = monsterstats::getMonsterStat('exp',$monsterID);
            $parameters{exp} = $monster_exp;
            my $exp_rem = stats::getStat('exp_rem',$userID);
            $exp_rem -= $monster_exp;
            if($exp_rem <= 0) {
                $exp_rem = 100;
                $parameters{level_up} = 1;
            }
            stats::setStat('exp_rem',$userID,$exp_rem);   		
		} else {
			# monster won	
			$parameters{lost} = 1;
		}
		$parameters{combat} = \@combat;
	} else {
		# running away - back to the index page!
		print $query->redirect('index.cgi');
	}	
} else {
    my $area_id = $arguments{'area'};
    $sth = $dbh->prepare("SELECT monster FROM area_monsters WHERE area = ? ORDER BY RAND() LIMIT 1");
    $sth->execute($area_id);
    my $monster_id;
    $sth->bind_columns(\$monster_id);
    $sth->fetch;
    $sth = $dbh->prepare("SELECT name FROM monsters WHERE id = ?");
    $sth->execute($monster_id);
    $sth->bind_columns(\$parameters{monster});
    $sth->fetch;
}
 
my $area_id = $query->url_param('area');
$sth = $dbh->prepare("SELECT name FROM areas WHERE id = ?");
$sth->execute($area_id);
$sth->bind_columns(\$parameters{area_name});
$sth->fetch;
 
my $template = HTML::Template->new(
		filename	=>	'explore.tmpl',
		associate	=>	$query,
	);
$template->param(%parameters);
print $query->header(), $template->output;

explore.tmpl:

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<html>
<head>
	<title>The <!--tmpl_var name='area_name'--></title>
</head>
<body>
	<tmpl_unless name='combat'>
		<p>You've encountered a <!--tmpl_var name='monster'-->!</p>
		<form action='explore.cgi?area=<!--tmpl_var name='area'-->' method='post'>
			<input type='submit' name='action' value='Attack' /> or 
			<input type='submit' name='action' value='Run Away' />
			<input type='hidden' name='monster' value='<!--tmpl_var name='monster'-->' />
		</form>
	<tmpl_else>
		<ul>
		<tmpl_loop name='combat'>
			<li><strong><!--tmpl_var name='attacker'--></strong> attacks <!--tmpl_var name='defender'--> for <!--tmpl_var name='damage'--> damage!</li>
		</tmpl_loop>
		</ul>
		<tmpl_if name='won'>
			<p>You killed <strong><!--tmpl_var name='monster'--></strong>! You gained <strong><!--tmpl_var name='gold'--></strong> gold, and <strong><!--tmpl_var name='exp'--></strong> experience.</p>
			<tmpl_if name='level_up'>
    			<p><strong>You gained a level!</strong></p>
			</tmpl_if>
			<p>You found a <strong><!--tmpl_var name='item'--></strong>!</p>
			<p><a href='explore.cgi?area=<!--tmpl_var name='area'-->'>Explore Again</a></p>
		</tmpl_if>
		<tmpl_if name='lost'>
			<p>You were killed by <strong><!--tmpl_var name='monster'--></strong>.</p>
		</tmpl_if>
		<p><a href='index.cgi'>Back to main</a></p>
	</tmpl_unless>
</body>
</html>

Extra Credit

  • Make the explore page verify that the area ID passed to explore.cgi actaully exists within the database(hint: SELECT COUNT).
]]> http://buildingbrowsergames.com/2009/01/19/implementing-multiple-areas-perl/feed/ 0 Adding Experience to our Combat System(Perl) http://buildingbrowsergames.com/2009/01/08/adding-experience-to-our-combat-systemperl/ http://buildingbrowsergames.com/2009/01/08/adding-experience-to-our-combat-systemperl/#comments Thu, 08 Jan 2009 14:00:38 +0000 Luke http://buildingbrowsergames.com/?p=673 I was recently e-mailed by Building Browsergames reader Mehmet Simsek – who noticed something that I completely missed: our combat system doesn’t have any experience or levelling built into it!

When a player kills a monster in the forest using our current codebase, they get gold and an item – but they don’t actually gain any experience(or levels) for killing the monster. Luckily for us, adding experience to our combat system is a quick (and fairly painless) task: we’ll start off by adding a few more stats to the database:

INSERT INTO stats(display_name, short_name) VALUES
    ('Experience','exp'),
    ('Experience Remaining', 'exp_rem');

We will use these two stats to keep track of the experience a player still needs for their next level, and the experience that a monster gives after it has been killed. Exactly what happens when a player levels up is up to you, the game developer.

We will also need to insert the values for the experience stat for our monsters into our database:

INSERT INTO entity_stats(stat_id,entity_id,value,entity_type) VALUES ((SELECT id FROM stats WHERE short_name='exp'),(SELECT id FROM monsters WHERE name='Crazy Eric'),5,'Monster');
INSERT INTO entity_stats(stat_id,entity_id,value,entity_type) VALUES ((SELECT id FROM stats WHERE short_name='exp'),(SELECT id FROM monsters WHERE name='Lazy Russell'),10,'Monster');
INSERT INTO entity_stats(stat_id,entity_id,value,entity_type) VALUES ((SELECT id FROM stats WHERE short_name='exp'),(SELECT id FROM monsters WHERE name='Hard Hitting Louis'),15,'Monster');

As you can see, we are inserting rows into our entity_stats table, so that each of the monsters in our game will give different amounts of experience. With these database changes made, it’s just a matter of opening up forest.cgi and making some changes:

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my $monster_exp = monsterstats::getMonsterStat('exp',$monsterID);
$parameters{exp} = $monster_exp;
my $exp_rem = stats::getStat('exp_rem',$userID);
$exp_rem -= $monster_exp;
if($exp_rem <= 0) {
    $exp_rem = 100;
    $parameters{level_up} = 1;
}
stats::setStat('exp_rem',$userID,$exp_rem);

You may have noticed that we’re setting some new variables for our template – so we’ll need to modify forest.tmpl as well:

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<p>You killed <strong><!--tmpl_var name='monster'--></strong>! You gained <strong><!--tmpl_var name='gold'--></strong> gold, and <strong><!--tmpl_var name='exp'--></strong> experience.</p>
<tmpl_if name='level_up'>
	<p><strong>You gained a level!</strong></p>
</tmpl_if>

With all your changes made, try playing your game – you should notice the message “You gained a level!” appearing whenever your character levels up.

Extra Credit

  • Change the forest template so that in the post-combat summary, the player will also be told how much experience remains before their next level.
  • Modify the code given so that your game will track the total experience a player has collected – and also display it on the main page.
]]> http://buildingbrowsergames.com/2009/01/08/adding-experience-to-our-combat-systemperl/feed/ 0 Dropping Items (Perl) http://buildingbrowsergames.com/2008/10/23/dropping-items-perl/ http://buildingbrowsergames.com/2008/10/23/dropping-items-perl/#comments Thu, 23 Oct 2008 14:00:29 +0000 Luke http://buildingbrowsergames.com/?p=520 Now that we’ve built a way for users to buy items, we need a way for users to get items – by killing monsters. Today, we’ll be adding drops to our combat system.

To begin with, check out a recent copy of the source code for our tutorial:

svn checkout http://building-browsergames-tutorial.googlecode.com/svn/trunk/perl/pbbg tutorial -r 42

In order to keep track of the items that our monsters drop, we need to add another table to our database:

CREATE TABLE monster_items (
	id int NOT NULL AUTO_INCREMENT,
	monster_id int,
	item_id int,
	rarity int,
	PRIMARY KEY(id)
);

The monster_items table will be what we use to keep track of the items that monsters can drop after users kill them. Most of this table explains itself – but you might be wondering about what the ‘rarity’ column is there for. Essentially, the ‘rarity’ column is there for exactly what it says it’s there for; defining the rarity of a drop! We will use the value in the column to randomly determine which items drop from a monster – allowing us to have item A at 10% rarity, and item B at 90% rarity from the same monster.

With our table created, let’s move on to writing some code. We’ll get the ball rolling with a slight tweak to forest.tmpl:

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<p>You found a <strong><!--tmpl_var name='item'--></strong>!</p>

We will be using that extra piece of code in our template to display the item that the user gains after killing the monster.

With our template tweaked, we can move on to writing some actual code inside forest.cgi:

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my $rand = int(rand(100));
$sth = $dbh->prepare("SELECT item_id FROM monster_items WHERE monster_id = ? AND rarity >= ? ORDER BY RAND() LIMIT 1");
$sth->execute($monsterID,$rand);
my $itemID;
$sth->bind_columns(\$itemID);
$sth->fetch;
$sth = $dbh->prepare("SELECT count(id) FROM user_items WHERE user_id = ? AND item_id = ?");
$sth->execute($userID,$itemID);
my $count;
$sth->bind_columns(\$count);
$sth->fetch;
if($count > 0) {
	# already has one of the item
	$sth = $dbh->prepare("UPDATE user_items SET quantity = quantity + 1 WHERE user_id = ? AND item_id = ?");
} else {
	# has none of the item - new row
	$sth = $dbh->prepare("INSERT INTO user_items(quantity,user_id,item_id) VALUES (1,?,?)");
}
$sth->execute($userID,$itemID);
$sth = $dbh->prepare("SELECT name FROM items WHERE id = ?");
$sth->execute($itemID);
$sth->bind_columns(\$parameters{item});
$sth->fetch;

If you’ve been paying attention, you might have noticed that this code is (for the most part), an exact copy of the code from our items shop from earlier. The only ‘new’ part of this code is the first 5 lines or so; it is there that we retrieve the new loot for the user. To begin with, we generate a random number between 0, and 100. While we don’t really need to pass the value through int(), it makes the number a lot simpler to work with(as it’s now 20, instead of 20.020859). Next, we use a single line of SQL to retrieve a random item for the player that is A) dropped by the monster, and B) has a rarity greater than or equal to the value that we randomly generated earlier. We use the ORDER BY RAND() clause to randomize within our results, and finally add LIMIT 1 to make sure that we only get one back. Once we’ve retrieved the random item to add to the player’s inventory, we’re finished – users can now received random items from the monsters that they kill in combat.

Here’s the updated forest.cgi:

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#!/usr/bin/perl -w
 
use strict;
use CGI qw(:cgi);
use HTML::Template;
use DBI;
use config;
 
my $query = new CGI;
my %arguments = $query->Vars;
 
my $dbh = DBI->connect("DBI:mysql:$config{dbName}:$config{dbHost}",$config{dbUser},$config{dbPass},{RaiseError => 1});
my $sth;
my %parameters;
 
if(%arguments) {
	if($arguments{action} eq 'Attack') {
		# fighting the monster	
		use stats;
		use monsterstats;
		my $cookie = $query->cookie('username+password'); 
		my ($username) = split(/\+/,$cookie);
		$sth = $dbh->prepare("SELECT id FROM users WHERE UPPER(username) = UPPER(?)");
		$sth->execute($username);
		my $userID;
		$sth->bind_columns(\$userID);
		$sth->fetch;
		my %player = (
			name		=>	$username,
			attack		=>	stats::getStat('atk',$userID),
			defence		=>	stats::getStat('def',$userID),
			curhp		=>	stats::getStat('curhp',$userID)
		);
		my $phand = stats::getStat('phand',$userID);
		$player{attack} += weaponstats::getWeaponStat('atk',$phand);
		use armorstats;
		my @armor = qw(atorso ahead alegs aright aleft);
		foreach my $key(@armor) {
			my $id = stats::getStat($key,$userID);
			my $defence = armorstats::getArmorStat('defence',$id);
			$player{defence} += $defence;
		}		
		$sth = $dbh->prepare("SELECT id FROM monsters WHERE name = ?");
		$sth->execute($arguments{monster});
		my $monsterID;
		$sth->bind_columns(\$monsterID);
		$sth->fetch;
		my %monster = (
			name		=>	$arguments{monster},
			attack		=>	monsterstats::getMonsterStat('atk',$monsterID),
			defence		=>	monsterstats::getMonsterStat('def',$monsterID),
			curhp		=>	monsterstats::getMonsterStat('maxhp',$monsterID)
		);
		my @combat;
		my $turns = 0;
		my ($attacker,$defender);
		while($player{curhp} > 0 && $monster{curhp} > 0) {
			my %attack;
			if($turns % 2 != 0) {
				$attacker = \%monster;
				$defender = \%player;
			} else {
				$attacker = \%player;
				$defender = \%monster;
			}
			my $damage = 0;
			if($attacker->{attack} > $defender->{defence}) {
				$damage = $attacker->{attack} - $defender->{defence};	
			}
			my %attack = (
				attacker => $attacker->{name},
				defender => $defender->{name},
				damage => $damage
			);
			$defender->{curhp} -= $damage;
			push @combat, \%attack;
			$turns++;
		}
		stats::setStat('curhp',$userID,$player{curhp});
		if($player{curhp} > 0) {
			# player won
			stats::setStat('gc',$userID,stats::getStat('gc',$userID) + monsterstats::getMonsterStat('gc',$monsterID));
			$parameters{won} = 1;
			$parameters{gold} = monsterstats::getMonsterStat('gc',$monsterID);
			my $rand = int(rand(99))+1;
			$sth = $dbh->prepare("SELECT item_id FROM monster_items WHERE monster_id = ? AND rarity >= ? ORDER BY RAND() LIMIT 1");
			$sth->execute($monsterID,$rand);
			my $itemID;
			$sth->bind_columns(\$itemID);
			$sth->fetch;
			$sth = $dbh->prepare("SELECT count(id) FROM user_items WHERE user_id = ? AND item_id = ?");
			$sth->execute($userID,$itemID);
			my $count;
			$sth->bind_columns(\$count);
			$sth->fetch;
			if($count > 0) {
				# already has one of the item
				$sth = $dbh->prepare("UPDATE user_items SET quantity = quantity + 1 WHERE user_id = ? AND item_id = ?");
			} else {
				# has none of the item - new row
				$sth = $dbh->prepare("INSERT INTO user_items(quantity,user_id,item_id) VALUES (1,?,?)");
			}
			$sth->execute($userID,$itemID);
			$sth = $dbh->prepare("SELECT name FROM items WHERE id = ?");
			$sth->execute($itemID);
			$sth->bind_columns(\$parameters{item});
			$sth->fetch;
		} else {
			# monster won	
			$parameters{lost} = 1;
		}
		$parameters{combat} = \@combat;
	} else {
		# running away - back to the index page!
		print $query->redirect('index.cgi');
	}	
} else {
	$sth = $dbh->prepare("SELECT name FROM monsters ORDER BY RAND() LIMIT 1");
	$sth->execute();
	my $monster;
	$sth->bind_columns(\$monster);
	$sth->fetch;
	$parameters{monster} = $monster;
}
 
 
my $template = HTML::Template->new(
		filename	=>	'forest.tmpl',
		associate	=>	$query,
	);
$template->param(%parameters);
print $query->header(), $template->output;

Extra Credit

  • Change the ‘you found an item’ message to also display the total quantity of the item that is in the user’s inventory.
]]> http://buildingbrowsergames.com/2008/10/23/dropping-items-perl/feed/ 0 Using Items (Perl) http://buildingbrowsergames.com/2008/10/17/using-items-perl/ http://buildingbrowsergames.com/2008/10/17/using-items-perl/#comments Fri, 17 Oct 2008 14:00:31 +0000 Luke http://buildingbrowsergames.com/?p=491 Our game is still missing something really important: items that users can actually use!

Today, we’ll be writing the code that allows our users to use the items in their inventory. To start off, check out a copy of the code for our project:

svn checkout http://building-browsergames-tutorial.googlecode.com/svn/trunk/perl/pbbg tutorial -r 38

And then we’re ready to go!

To start off, we’ll build a basic template for our inventory page, and put it inside inventory.tmpl:

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<html>
<head>
	<title>Your Inventory</title>
</head>
<body>
	<p>This is your inventory. Check out all the stuff you've got!</p>
	<tmpl_if name='message'>
		<p><!--tmpl_var name='message'--></p>
	</tmpl_if>
	<ul>
		<tmpl_loop name='inventory'>
		<li>
			<strong><!--tmpl_var name='name'--> x <!--tmpl_var name='quantity'--></strong>
			<form action='inventory.cgi' method='post'>
				<input type='hidden' name='item-id' value='<!--tmpl_var name="id"-->' />
				<input type='submit' value='Use' />
			</form>
		</li>
		</tmpl_loop>
	</ul>
</body>
</html>

With our template built, we can start writing the code inside inventory.cgi:

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#!/usr/bin/perl -w
 
use strict;
use CGI qw(:cgi);
use CGI::Carp qw(fatalsToBrowser warningsToBrowser);
use HTML::Template;
use DBI;
use config;
 
my $query = new CGI;
my %arguments = $query->Vars;
 
my $dbh = DBI->connect("DBI:mysql:$config{dbName}:$config{dbHost}",$config{dbUser},$config{dbPass},{RaiseError => 1});
my $sth;
my %parameters;
 
use stats;
 
my $cookie = $query->cookie('username+password');
my ($username) = split(/\+/,$cookie);
$sth = $dbh->prepare("SELECT id FROM users WHERE UPPER(username) = UPPER(?)");
$sth->execute($username);
my $userID;
$sth->bind_columns(\$userID);
$sth->fetch;
 
$sth = $dbh->prepare("SELECT item_id, quantity FROM user_items WHERE user_id = ?");
$sth->execute($userID);
my @inventory = ();
while(my $row = $sth->fetchrow_hashref) {
	my $sth2 = $dbh->prepare("SELECT name FROM items WHERE id = ?");
	$sth2->execute($row->{item_id});
	$sth2->bind_columns(\$row->{name});
	$sth2->fetch;
	push @inventory, $row;
}
 
$parameters{inventory} = \@inventory;
 
my $template = HTML::Template->new(
		filename	=>	'inventory.tmpl',
		associate	=>	$query,
		die_on_bad_params => 0,
	);
$template->param(%parameters);
print $query->header(), $template->output;

This code is almost entirely from our item shop code – so there isn’t really anything you haven’t seen before. The one new piece is the die_on_bad_params parameter that we are passing to HTML::Template->new() – we do this so that it won’t complain about the fact that our @inventory variable has the value ‘item_id’ inside of it, but the template doesn’t.

Our code is still missing something, however: the ability to actually use items!

If you remember the initial database preparations that we did earlier, you’ll remember that we created a new stat called ‘Item Use Token’ – and now we’ll be putting that stat to use. We will be using the ‘Item Use Token’ stat in conjunction with what’s known as a Dispatch Table to easily write the code that will run when our items are used.

For now, we’ll insert a single item with the token ‘potion’:

INSERT INTO items(name,type,price) VALUES ('Red Potion','Usable',10);
	INSERT INTO entity_stats(stat_id,entity_id,value,entity_type) VALUES ((SELECT id FROM stats WHERE short_name='token'),(SELECT id FROM items WHERE name='Red Potion'),'potion','Item');

With that stat set up, we can buckle down and start on our dispatch table.

Dispatch tables are one of the more useful tools available to you as a programmer; they allow you to create a hash of functions(instead of values), and then call functions by key. This makes them perfect for our items system, because using dispatch tables will allow us to easily add new code for items in the most efficient manner possible. Let’s write some code to define and interact with a dispatch table:

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my %actions = (
	'potion' => \&use_potion,
);
 
sub use_potion {
	$parameters{message} = 'This is code that would run if the user used a potion.';
}
 
if(%arguments) {
	if($arguments{'item-id'}) {
		use items;
		$sth = $dbh->prepare("SELECT item_id FROM user_items WHERE user_id = ? AND id = ?");
		$sth->execute($userID,$arguments{'item-id'});
		my $itemID;
		$sth->bind_columns(\$itemID);
		$sth->fetch;
		my $token = items::getStat('token',$itemID);
		$actions{$token}->();
	}
}

If you visit your inventory page and click on ‘Use’ underneath the item in your character’s inventory, you should be treated to the simple message ‘This is code that would run when the user used a potion’. Neat, eh?

While we’ve built the functionality for a single item, that’s not really our use-case – we need to see how useful this system will be if we want to add another item without writing too much extra code. Ideally, we would only need to write the code that makes this item special – and thankfully, dispatch tables let us do just that. First, we’ll add another item, with the token ‘crystal_ball’:

INSERT INTO items(name,type,price) VALUES ('Crystal Ball','Usable',10);
	INSERT INTO entity_stats(stat_id,entity_id,value,entity_type) VALUES ((SELECT id FROM stats WHERE short_name='token'),(SELECT id FROM items WHERE name='Crystal Ball'),'crystal_ball','Item');

And now that we’ve added the item, we’ll add the code to run when an item with that token gets used:

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my %actions = (
	'potion' => \&use_potion,
	'crystal_ball'	=>	\&use_crystal_ball,
);
 
sub use_crystal_ball {
	$parameters{message} = 'This is code that would run if the user used a crystal ball.';
}

And if you use the crystal ball now that we’ve written that code, you’ll see the message ‘This is code that would run if the user used a crystal ball.’.

The ability to keep our code organized in this way is what makes dispatch tables so useful – it doesn’t take us long at all to write more code to support any new items we want to add, and it’s as simple as just adding a new token(which serves as a key in the dispatch table), and then writing the function that will be called(you could even map multiple tokens to the same function, if you wanted to – although in that situation you should just have two items with the same token).

And with that, our inventory page is complete! Users can now use any items that you have defined tokens and written the code for – and you can run any code that should be executed no matter what the item’s token is by adding it just after the line that says:

$actions{$token}->();

Here’s the (slightly re-organized) code for inventory.cgi:

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#!/usr/bin/perl -w
 
use strict;
use CGI qw(:cgi);
use CGI::Carp qw(fatalsToBrowser warningsToBrowser);
use HTML::Template;
use DBI;
use config;
 
my $query = new CGI;
my %arguments = $query->Vars;
 
my $dbh = DBI->connect("DBI:mysql:$config{dbName}:$config{dbHost}",$config{dbUser},$config{dbPass},{RaiseError => 1});
my $sth;
my %parameters;
 
use stats;
 
my $cookie = $query->cookie('username+password');
my ($username) = split(/\+/,$cookie);
$sth = $dbh->prepare("SELECT id FROM users WHERE UPPER(username) = UPPER(?)");
$sth->execute($username);
my $userID;
$sth->bind_columns(\$userID);
$sth->fetch;
 
my %actions = (
	'potion' => \&use_potion,
	'crystal_ball'	=>	\&use_crystal_ball,
);
 
sub use_crystal_ball {
	$parameters{message} = 'This is code that would run if the user used a crystal ball.';
}
 
sub use_potion {
	$parameters{message} = 'This is code that would run if the user used a potion.';
}
 
if(%arguments) {
	if($arguments{'item-id'}) {
		use items;
		$sth = $dbh->prepare("SELECT item_id FROM user_items WHERE user_id = ? AND id = ?");
		$sth->execute($userID,$arguments{'item-id'});
		my $itemID;
		$sth->bind_columns(\$itemID);
		$sth->fetch;
		my $token = items::getStat('token',$itemID);
		$actions{$token}->();
	}
}
 
$sth = $dbh->prepare("SELECT id, item_id, quantity FROM user_items WHERE user_id = ?");
$sth->execute($userID);
my @inventory = ();
while(my $row = $sth->fetchrow_hashref) {
	my $sth2 = $dbh->prepare("SELECT name FROM items WHERE id = ?");
	$sth2->execute($row->{item_id});
	$sth2->bind_columns(\$row->{name});
	$sth2->fetch;
	push @inventory, $row;
}
 
$parameters{inventory} = \@inventory;
 
my $template = HTML::Template->new(
		filename	=>	'inventory.tmpl',
		associate	=>	$query,
		die_on_bad_params => 0,
	);
$template->param(%parameters);
print $query->header(), $template->output;

And here’s inventory.tmpl:

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<html>
<head>
	<title>Your Inventory</title>
</head>
<body>
	<p>This is your inventory. Check out all the stuff you've got!</p>
	<tmpl_if name='message'>
		<p><!--tmpl_var name='message'--></p>
	</tmpl_if>
	<ul>
		<tmpl_loop name='inventory'>
		<li>
			<strong><!--tmpl_var name='name'--> x <!--tmpl_var name='quantity'--></strong>
			<form action='inventory.cgi' method='post'>
				<input type='hidden' name='item-id' value='<!--tmpl_var name="id"-->' />
				<input type='submit' value='Use' />
			</form>
		</li>
		</tmpl_loop>
	</ul>
</body>
</html>

Extra Credit

  • Re-factor the weapons and armor systems, so that they are all sold from the item-shop – and when you use them from your inventory, the items are equipped.
]]> http://buildingbrowsergames.com/2008/10/17/using-items-perl/feed/ 0 Buying Items (Perl) http://buildingbrowsergames.com/2008/10/14/buying-items-perl/ http://buildingbrowsergames.com/2008/10/14/buying-items-perl/#comments Tue, 14 Oct 2008 14:00:31 +0000 Luke http://buildingbrowsergames.com/?p=484 We’ve already run the initial database code to get our items system prepared, and now it’s time to write the code that is responsible for interacting with it. Today, we’ll build the items shop.

In order to get started, check out a copy of our code from the Google Code Project:

svn checkout http://building-browsergames-tutorial.googlecode.com/svn/trunk/perl/pbbg tutorial -r 36

With that done, we’re ready to get started building our item system!

For starters, we’ll build an item shop – because we need players to be able to get items into their inventory before they can interact with them. We’ll start off with just about the same template code as we had for our armor and weapons shops, inside of item-shop.tmpl:

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<html>
<head>
	<title>The Item Shop</title>
</head>
<body>
	<p>Welcome to the Item Shop.</p>
	<p><a href='index.cgi'>Back to main</a></p>
	<h3>Current Inventory:</h3>
	<ul>
		<tmpl_loop name='inventory'>
		<li>
			<!--tmpl_var name='name'--> x <!--tmpl_var name='quantity'-->
			<form action='item-shop.cgi' method='post'>
				<input type='hidden' name='sell' value='<!--tmpl_var name="item_id"-->' />
				<input type='submit' value='Sell' />
			</form>
		</li>
		</tmpl_loop>
	</ul>
	<p>You may purchase any of the items listed below.</p>
	<tmpl_if name='error'>
		<p style='color:red'><!--tmpl_var name='error'--></p>
	</tmpl_if>
	<tmpl_if name='message'>
		<p style='color:green'><!--tmpl_var name='message'--></p>
	</tmpl_if>
	<ul>
		<tmpl_loop name='items'>
			<li>
				<strong><!--tmpl_var name='name'--></strong> - <em><!--tmpl_var name='price'--> gold coins</em>
				<form action='item-shop.cgi' method='post'>
					<input type='hidden' name='item-id' value='<!--tmpl_var name="id"-->' />
					<input type='submit' value='Buy' />
				</form>
			</li>
		</tmpl_loop>
	</ul>
</body>
</html>

This is essentially the same template as our other shops – the only difference is the ‘Current Inventory’ display. The current inventory is pretty self-explanatory; it will display the user’s current inventory whenever they visit the shop. Let’s start writing the code for our shop, inside item-shop.cgi:

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#!/usr/bin/perl -w
 
use strict;
use CGI qw(:cgi);
use CGI::Carp qw(fatalsToBrowser warningsToBrowser);
use HTML::Template;
use DBI;
use config;
 
my $query = new CGI;
my %arguments = $query->Vars;
 
my $dbh = DBI->connect("DBI:mysql:$config{dbName}:$config{dbHost}",$config{dbUser},$config{dbPass},{RaiseError => 1});
my $sth;
my %parameters;
 
use stats;
 
my $cookie = $query->cookie('username+password');
my ($username) = split(/\+/,$cookie);
$sth = $dbh->prepare("SELECT id FROM users WHERE UPPER(username) = UPPER(?)");
$sth->execute($username);
my $userID;
$sth->bind_columns(\$userID);
$sth->fetch;
 
$sth = $dbh->prepare("SELECT DISTINCT(id), name, price FROM items WHERE type = 'Usable' LIMIT 5");
$sth->execute();
my @items = ();
while(my $row = $sth->fetchrow_hashref) {
	push @items, $row;
}
 
$sth = $dbh->prepare("SELECT item_id, quantity FROM user_items WHERE user_id = ?");
$sth->execute($userID);
my @inventory = ();
while(my $row = $sth->fetchrow_hashref) {
	my $sth2 = $dbh->prepare("SELECT name FROM items WHERE id = ?");
	$sth2->execute($row->{item_id});
	$sth2->bind_columns(\$row->{name});
	$sth2->fetch;
	push @inventory, $row;
}
 
$parameters{inventory} = \@inventory;
$parameters{items} = \@items;
 
my $template = HTML::Template->new(
		filename	=>	'item-shop.tmpl',
		associate	=>	$query,
	);
$template->param(%parameters);
print $query->header(), $template->output;

For the most part, this is all code we’ve written before. The only ‘new’ code here is the inventory retrieval code, on lines 36-43. We retrieve all of the rows in user_items that are linked to the current user, and then store them into our @inventory array so that we can display them. We also retrieve and store the name of the item, so that it will display with something a little easier for the player to understand than ‘18′(which is currently a ‘Red Potion’ in the sample game).

Now that we can display items, we should write some code so users can buy them:

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if(%arguments) {
	if($arguments{'item-id'}) {
		my $itemID = $arguments{'item-id'};
		$sth = $dbh->prepare("SELECT price FROM items WHERE id = ?");
		$sth->execute($itemID);
		my $price;
		$sth->bind_columns(\$price);
		$sth->fetch;
		my $gold = stats::getStat('gc',$userID);
		if($gold >= $price) {
			stats::setStat('gc',$userID,($gold - $price));
			$sth = $dbh->prepare("SELECT count(id) FROM user_items WHERE user_id = ? AND item_id = ?");
			$sth->execute($userID,$itemID);
			my $count;
			$sth->bind_columns(\$count);
			$sth->fetch;
			if($count > 0) {
				# already has one of the item
				$sth = $dbh->prepare("UPDATE user_items SET quantity = quantity + 1 WHERE user_id = ? AND item_id = ?");
			} else {
				# has none of the item - new row
				$sth = $dbh->prepare("INSERT INTO user_items(quantity,user_id,item_id) VALUES (1,?,?)");
			}
			$sth->execute($userID,$itemID);
			$parameters{message} = 'You purchased the item.';
		} else {
			$parameters{error} = 'You cannot afford that item!';
		}		
	}
}

If you’re comparing this to the code from our weapons or armor shops from earlier, you might notice some differences – like the fact that we’re running two queries to add items to the player’s inventory, instead of just one. This is because our user inventory has been built in such a way that items can ’stack’ – meaning you can have more than one of any particular item. Because we only need to keep track of the fact that a player has <x> of an item, we just use a column inside user_items to keep track of the quantity of the item that the player currently has in their inventory. Because we’re storing our data in this way, whenever we want to add an item to a player’s inventory, we need to first check and see if a row exists – if it does, we increment the quantity of the item. If it doesn’t, we’ll insert a new row.

Now that that’s finished, there’s only one more thing our item shop is missing – the ability to sell items! We’ll quickly add our item selling code to item-shop.cgi:

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} elsif($arguments{sell}) {
	my $itemID = $arguments{sell};
	$sth = $dbh->prepare("SELECT price FROM items WHERE id = ?");
	$sth->execute($itemID);
	my $price;
	$sth->bind_columns(\$price);
	$sth->fetch;
	my $gold = stats::getStat('gc',$userID);
	stats::setStat('gc',$userID,($gold + $price));
	$sth = $dbh->prepare("SELECT quantity FROM user_items WHERE user_id = ? AND item_id = ?");
	$sth->execute($userID,$itemID);
	my $quantity;
	$sth->bind_columns(\$quantity);
	$sth->fetch;
	if($quantity > 1) {
		$sth = $dbh->prepare("UPDATE user_items SET quantity = quantity - 1 WHERE user_id = ? AND item_id = ?");
	} else {
		$sth = $dbh->prepare("DELETE FROM user_items WHERE user_id = ? AND item_id = ?");
	}
	$sth->execute($userID,$itemID);
	$parameters{message} = 'You sold the item.';
}

This code is pretty similar to the code from our other shops, except for the different method used to update the information in the database. In the ‘buy item’ code(2 blocks above), we used ‘SELECT COUNT’ to check to see if a row existed – in this case, because we need to see how many of the item the player has, we just use a ‘SELECT’ statement to retrieve the quantity of the item that the player has. Based on the value we retrieve, we perform one of two queries – an UPDATE query if they have more than 1, and a DELETE query if they have only 1 of the item. Performing the DELETE query removes the row from the user_items table, which helps us make sure that we are only storing data we need.

With that code written, we’re done! We have a working item shop now, and our inventory system is beginning to take shape. Don’t forget to link to it from your main page:

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<p><a href='item-shop.cgi'>The Item Shop</a></p>

And that’s that! Here’s the code from item-shop.tmpl:

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<html>
<head>
	<title>The Item Shop</title>
</head>
<body>
	<p>Welcome to the Item Shop.</p>
	<p><a href='index.cgi'>Back to main</a></p>
	<h3>Current Inventory:</h3>
	<ul>
		<tmpl_loop name='inventory'>
		<li>
			<!--tmpl_var name='name'--> x <!--tmpl_var name='quantity'-->
			<form action='item-shop.cgi' method='post'>
				<input type='hidden' name='sell' value='<!--tmpl_var name="item_id"-->' />
				<input type='submit' value='Sell' />
			</form>
		</li>
		</tmpl_loop>
	</ul>
	<p>You may purchase any of the items listed below.</p>
	<tmpl_if name='error'>
		<p style='color:red'><!--tmpl_var name='error'--></p>
	</tmpl_if>
	<tmpl_if name='message'>
		<p style='color:green'><!--tmpl_var name='message'--></p>
	</tmpl_if>
	<ul>
		<tmpl_loop name='items'>
			<li>
				<strong><!--tmpl_var name='name'--></strong> - <em><!--tmpl_var name='price'--> gold coins</em>
				<form action='item-shop.cgi' method='post'>
					<input type='hidden' name='item-id' value='<!--tmpl_var name="id"-->' />
					<input type='submit' value='Buy' />
				</form>
			</li>
		</tmpl_loop>
	</ul>
</body>
</html>

And here’s the (slightly tweaked) code from item-shop.cgi:

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#!/usr/bin/perl -w
 
use strict;
use CGI qw(:cgi);
use CGI::Carp qw(fatalsToBrowser warningsToBrowser);
use HTML::Template;
use DBI;
use config;
 
my $query = new CGI;
my %arguments = $query->Vars;
 
my $dbh = DBI->connect("DBI:mysql:$config{dbName}:$config{dbHost}",$config{dbUser},$config{dbPass},{RaiseError => 1});
my $sth;
my %parameters;
 
use stats;
 
my $cookie = $query->cookie('username+password');
my ($username) = split(/\+/,$cookie);
$sth = $dbh->prepare("SELECT id FROM users WHERE UPPER(username) = UPPER(?)");
$sth->execute($username);
my $userID;
$sth->bind_columns(\$userID);
$sth->fetch;
 
if(%arguments) {
	my $price;
	my $itemID;
	$itemID = $arguments{'item-id'} ? $arguments{'item-id'} : $arguments{sell};
	$sth = $dbh->prepare("SELECT price FROM items WHERE id = ?");
	$sth->execute($itemID);
	$sth->bind_columns(\$price);
	$sth->fetch;
	my $gold = stats::getStat('gc',$userID);
	if($arguments{'item-id'}) {
		if($gold >= $price) {
			stats::setStat('gc',$userID,($gold - $price));
			$sth = $dbh->prepare("SELECT count(id) FROM user_items WHERE user_id = ? AND item_id = ?");
			$sth->execute($userID,$itemID);
			my $count;
			$sth->bind_columns(\$count);
			$sth->fetch;
			if($count > 0) {
				# already has one of the item
				$sth = $dbh->prepare("UPDATE user_items SET quantity = quantity + 1 WHERE user_id = ? AND item_id = ?");
			} else {
				# has none of the item - new row
				$sth = $dbh->prepare("INSERT INTO user_items(quantity,user_id,item_id) VALUES (1,?,?)");
			}
			$sth->execute($userID,$itemID);
			$parameters{message} = 'You purchased the item.';
		} else {
			$parameters{error} = 'You cannot afford that item!';
		}		
	} elsif($arguments{sell}) {
		stats::setStat('gc',$userID,($gold + $price));
		$sth = $dbh->prepare("SELECT quantity FROM user_items WHERE user_id = ? AND item_id = ?");
		$sth->execute($userID,$itemID);
		my $quantity;
		$sth->bind_columns(\$quantity);
		$sth->fetch;
		if($quantity > 1) {
			$sth = $dbh->prepare("UPDATE user_items SET quantity = quantity - 1 WHERE user_id = ? AND item_id = ?");
		} else {
			$sth = $dbh->prepare("DELETE FROM user_items WHERE user_id = ? AND item_id = ?");
		}
		$sth->execute($userID,$itemID);
		$parameters{message} = 'You sold the item.';
	}
}
 
$sth = $dbh->prepare("SELECT DISTINCT(id), name, price FROM items WHERE type = 'Usable' LIMIT 5");
$sth->execute();
my @items = ();
while(my $row = $sth->fetchrow_hashref) {
	push @items, $row;
}
 
$sth = $dbh->prepare("SELECT item_id, quantity FROM user_items WHERE user_id = ?");
$sth->execute($userID);
my @inventory = ();
while(my $row = $sth->fetchrow_hashref) {
	my $sth2 = $dbh->prepare("SELECT name FROM items WHERE id = ?");
	$sth2->execute($row->{item_id});
	$sth2->bind_columns(\$row->{name});
	$sth2->fetch;
	push @inventory, $row;
}
 
$parameters{inventory} = \@inventory;
$parameters{items} = \@items;
 
my $template = HTML::Template->new(
		filename	=>	'item-shop.tmpl',
		associate	=>	$query,
	);
$template->param(%parameters);
print $query->header(), $template->output;

Extra Credit

  • Can you modify the item shop so that it sells all types of items?
]]> http://buildingbrowsergames.com/2008/10/14/buying-items-perl/feed/ 0 Integrating Armor into our combat system (Perl) http://buildingbrowsergames.com/2008/09/30/integrating-armor-into-our-combat-system-perl/ http://buildingbrowsergames.com/2008/09/30/integrating-armor-into-our-combat-system-perl/#comments Tue, 30 Sep 2008 14:00:30 +0000 Luke http://buildingbrowsergames.com/?p=429 We now have a way for our users to buy armor, but we haven’t made it so that the armor a user has equipped affects anything – at least, not yet. Today, we’ll be modifying our combat system so that a user’s armor affects the damage they take(just like we did with our weapons system earlier).

Because we’ve already written the stats retrieval code for our armor system, there isn’t much left to do but add the relevant code to forest.cgi:

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use armorstats;
my @armor = qw(atorso ahead alegs aright aleft);
foreach my $key(@armor) {
	my $id = stats::getStat($key,$userID);
	my $defence = armorstats::getArmorStat('defence',$id);
	$player{defence} += $defence;
}

And that’s actually all there is to it! If you visit the forest page with some armor equipped now, you should notice the defence value of your equipped armor taking effect.

Extra Credit

  • Make the combat system display all of the modifiers in the fight(e.g. – “5 attack + 5 attack from sword, 2 defense + 3 defense from torso armor”).
]]> http://buildingbrowsergames.com/2008/09/30/integrating-armor-into-our-combat-system-perl/feed/ 3