This article concerns Halo 3's Forge map editor. For full reviews of Halo 3 itself, check out our Halo 3 campaign review and Halo 3 multiplayer review.

If you're a Halo fan, by this point you have surely heard at least something about Forge, the map-tweaking utility Bungie is including out of the box with Halo 3. At first glance, it seems like a very limited tool. You cannot edit any fundamental map geometry, you can only place or remove various accoutrements such as weapons and vehicles, crates and other ornamentation, spawn points and objectives, and so on.

Don't trust that first glance, however--it only scratches the surface of what is truly available when you start to delve deep into Forge. Though, for obvious reasons, Bungie has chosen to limit the scope of your individual additions to the supplied standard maps, the combined effects of these additions in creative ways can produce maps and games that play radically differently than anything offered officially.

How, you ask? Read on.

Hammer and Anvil

At the most basic level, Forge allows you to open up a standard Halo 3 map and add elements from a variety of categories--weapons, decorative elements, vehicles, new pickups such as the bubble shield and energy drain as seen in the multiplayer beta, gravity lifts, one- or two-way teleporters, spawn points, and so on. Essentially, these are all the things that can change on a given map depending on the gametype and other settings, but in Halo 3 you have fine control over all of them yourself.

Items can be rotated and stacked, and large simple objects like crates make for great building blocks. Many players will surely start off with simple tweaks like filling a map with rocket lauchers and grenades for a chaotic game, removing all excess weapons and ammo for a more conservative game, blocking doorways with large objects to alter the flow of a map, and so on.

By combining elements, such as placing a crate directly above a grav lift, you can create new unusual objects. A row of such combinations might create a floating, undulating "bridge" that could be used to get from one high perch to another. Taking that idea even further, one starts to imagine more ambitious ideals like a complex obstacle course such as one might see in a 3D platformer, with checkpoints placed at key areas along the set route.

Scrimping and Saving

To ensure that Forge-created levels never run into memory or performance issues, you are given a total budget which you use to spend on the elements you place--each element is assigned a dollar value, and also has a total overall hard limit per map.

For example, simple crates might cost only $2 each with a map limit of eight, while large Wraith tanks might cost $40 a pop with a map limit of two. Certain maps simply do not allow certain vehicles, for size reasons--smaller maps might disallow tanks entirely.

Overall budgets are in the range of hundreds of dollars, and you can always get extra cash by deleting extraneous decorative elements already placed on the map by default, so it does seem like there is a great deal of room for creativity before you start exhausting the practical limits.

Swiss Army Knife
One particularly clever placeable object is known simply as the custom powerup. On its own, the custom powerup is nothing but a blank slate. Its properties are actually determined in the custom gametype settings, which allows you to tie the same map to different gametypes while retaining different custom powerups for each depending on the needs of the gametype.

The remarkable and enticing thing about the custom powerup is that it really is what its name implies. The number and scope of simultaneous attributes that the pickup can assign to the player who acquires it--you can decide how long these attributes last, from 3-90 seconds--is absolutely staggering.

There's a lot to cover with this baby, so let's just get going. For one thing, you can modify the shield and health settings--how much damage resistance it provides, what shield multiplier it gives, if it removes the shield, if it raises or lowers shield recharge rate and by how much, if the player's shield recharges when the player causes damage, if the player is headshot immune.

Similarly, it can affect weapon stats--modifying damage caused from 0%-300% or even to insta-kill status, if grenades regenerate or ammo is infinite, if weapon pickup is disabled.

The powerup can raise or lower movement speed, adjust the pull of gravity to be greater or less, forbid or allow vehicle usage in different ways, modify the player sensor's range and ability to detect friends and foes, and even modify the player's physical appearance to be a different color, apply different levels of cloaking, or apply different types of waypoints to the player.

Batter Up
The obvious use of the custom powerup is of course as a coveted stat boost item, or even as a crippling curse cleverly placed in a highly-trafficked corridor to spice up a game of deathmatch. Of course, it can be used in much more unorthodox ways.

One custom user-made gametype mentioned by Bungie's Frank O'Connor, involves playing baseball with rockets (the balls) and gravity hammers (the bats) as well as checkpoints for bases; a special "batter" powerup might boost run speed and shields to give the player more of a fighting chance to make it around the bases alive.

Keep it Simple, Stupid
You don't need fancy stuff like the custom powerup to make some interesting custom games. Just with the gametype editor, you could easily devise any number of skill-pushing Slayer variants. For example, points might only be awarded for headshots, allowing you and your gaming group to hone your killer instincts before sticking it to the online matchmade players.

You might also work on your efficiency by detracting a point for every death, meaning the winner of the match will be the player with the highest spread between kills and deaths--sure, that statistic is tracked in regular games, but why not use it as a victory condition? The enormous amount of control over how points are awarded and in what quantity open up the doors to a wealth of simple but useful quick hacks.

So how can you take it further? Read on to find out.