I characterize depth as game systems or balance details that are included to enrich the experience of the player, but that are not necessarily explained or documented. They’re meant to be discovered and exploited as players’ expertise with the game grows.

There are lots of great examples of what I’m talking about in all types of games, but I will offer up a couple of made-up examples for illustration:

Example Game 1 is Wizard Warts, a fantasy role-playing game about a cabal of magical toads set deep in a haunted swamp. Pollywogs evolve into acolytes - able to hop, swim, wear armor and use weapons. But once they grow strong enough in the shallow waters around their home, they can quest deep into the swamp to find and eat one of the legendary magic Dragon-Flies.

Four different types of Dragon-Fly swarms live in the swamp: Fire, Ice, Poison/Acid and Love. Once a toad gobbles one of them up, the acolyte evolves into a Toadzard, and can thereafter belch spells powered by the type of bug-dragon they gobbled. It’s important to note that an acolyte toad can only gobble one type of magic Dragon-Fly in their life, and the choice (and the evolution into Toadzard) is irreversible.

The swamp is filled with a variety of magical monsters. They are all dangerous and hostile, but we can use the data of the game to add more depth to the gameplay. For example there are Plant type monsters are more vulnerable to Fire magic and take x3 damage from any source with that description, while Undead creatures are immune to Poison spells.

Notice that one of the Dragon-Flies has two “type” descriptions – Poison/Acid. I chose to include the "acid" description as part of that spell group because of the depth that I wanted to include in the design. Acquiring spell powers and evolving into a Toadzard would be a big part of the fun in the game. But if the player chooses "poison" spells and finds that they are literally useless against undead monsters, and "poison" was the only type of damage in that spell category, it could leave an entire class of Toadzard useless in some situations. That’s a very un-fun outcome to players who chose to build that type of character, and it might make the game unexpectedly difficult. Consider the example of player who decided to make their Toadzard Poison/Acid and then had to take on a tough mission against Undead bad guys. A player running into that situation might have so much difficulty that they abandon the game, and who could blame them?

Dropping some "acid" in helps solve these problems. "Acid" spells could still damage undead, leaving us the freedom to make "poison" spells useless against them. At this point you might reasonably ask; "Why fight so hard to preserve that part of the design at all?" The answer is that there is a lot of potential drama in the design that occasionally makes spells useless. It aggressively forces the player to adapt their comfortable play patterns, and it might encourage players to explore more of the content in the game. Imagine the player who finds themselves in a scary predicament when the spells and strategies that they've previously counted on suddenly stop working entirely. But, as they dig into the fullness of the spell systems they find that there is a way for them to adapt to the game situation without having to start over from the beginning.

A less aggressive way to achieve a similar effect would be to extend the Fire example above, and only give the monsters vulnerability to some types of spells. So for example we could include Hate type monsters that were vulnerable to Love magic and Lava type monsters that were vulnerable to Ice magic. Anyone familiar with the Pokemon series of games will recognize this precise design. It doesn't penalize players as harshly as the proposed design above, but it's also not as dramatic in the player's experience.

Ok, time for a POP QUIZ. What do you do, hotshot? What do you do?

Here’s a quiz to test your understanding of depth versus base game mechanics. Below is a description of another imaginary game. Give it a read, and then see if you can identify what parts of the design are game mechanics (the basic rules of the game) and what parts are included to add depth (discoverable elements of gameplay for master players).

Example Game 2 is Lucy Loogie, a side-scrolling platform game featuring a shifty urchin girl who can defeat enemies by spitting on them, or by jumping on their heads.

Any resemblance of the character to the actress Lucy Liu is purely coincidental.

The player can jump, or double jump controlled by a button press, or they can trigger Lucy’s spit, and it will travel in a short arc in the direction that she is facing.

Lucy’s path forward is blocked by a variety of enemies. Hitting them with a spit blob will defeat them, scoring points. But, if a spit blob hits the ground it leaves a slippery puddle behind for a few moments. If an enemy moves over a spit puddle, the bad guy loses their footing and slides uncontrollably across the ground. As they are sliding, they will run over other enemies, stunning them briefly in place. If a sliding enemy bumps into a hazard then they are stunned and immobile themselves for a short time.

Players start with 3 lives. The player earns points for every enemy they defeat, and if the player reaches 100 points they earn an extra life. If Lucy jumps on enemies that are stunned, the player scores bonus points, and if they can jump on multiple stunned enemies in sequence, they earn a multiplier bonus on their points which goes up by one for each successive enemy defeated (x1, x2, x3 etc.)

POP QUIZ ANSWERS   (warning - - - spoilers)

Do you say that the ability to leave little puddles of slippery spit was an example of adding depth to the game?

Wrong! And here’s why:

I would consider the spit puddle gameplay a core mechanic of the design. The slippery bad guys are so fundamental to the gameplay that I can imagine Lucy Loogie level layouts featuring setups based around the mechanic. For example, imagine a level where the player had to stun bad guys in a particular spot to make a tough jump. The spit puddles also lend themselves to designing bad guys around the feature. Picture a type of enemy holding an umbrella at a jaunty angle, and so is immune to spitting from one direction.

No, the depth of the Lucy Loogie design would be the points multiplier for defeating stunned enemies. (but I would be open to debating this in the comments section on my blog) Greater scores and more extra lives aren't necessary to the core design of the game. But it is a feature that is exploitable by expert players, and with mastery it can radically change their experience of playing the game both in terms of rewards and in how they approach game situations that they encounter.

The interesting, and sometimes wildly frustrating thing about depth in a design is that some players never become aware of the underlying nuances. In fact there are countless examples where depth is built into games, but players don’t understand it or take advantage of it. Multiplayer games suffer the most from this kind of mismatch in player expertise, because the parts of their community that grasp the deeper elements of the design and use them often have a significant advantage over the less-knowledgeable. This can lead to all sorts of hard feelings. (if you’re a League of Legends fan, last hitting creeps should spring immediately to mind)

As I mentioned earlier, depth in the game balance can exist without being documented anywhere else. Players will feel the effects as they play and hopefully they’ll pick up on the subtleties and learn how to exploit the design. But for that to work well the design needs to make some kind of intuitive sense to the player. In the Wizard Warts example, the player would glean that Fire is extra dangerous to plants. That's a common trope in games and of course; wood burns. But the underlying logic that "poison" wouldn’t have an effect on the Undead since they don’t have a working nervous system or circulatory system is less obvious, and so might never make sense to the player base. If the game is popular enough, the players will learn how the numbers work and "play around" them, but they're liable to think there's some kind of a bug in the game.

So to recap: We need a mental model with an underlying design for depth which is (hopefully) intuitive to the player. Which brings me back to the multiplayer weapons design process for Halo.

I’ll explain how it all connects in my next post!

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