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Designing an RPG Inventory System That Fits: Echoes of Eternea

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It's time for me to put my Gil where my mouth is and start applying the design tips and guidelines outlined in my previous article to a real-world case study, where I use my own recommended processes to design an inventory system for the high-fantasy, nostalgic RPG Echoes of Eternea.

As a reminder, in the previous segment, we discussed the most widely used RPG inventory systems, looking throughout at their perceived strengths and weaknesses. We then shifted gears to design, presenting preliminary questions you should ask yourself before committing to any one paradigm. By taking the time to evaluate which inventory system works best in your RPG, you'll have a much clearer picture of what direction, or combination of directions they should proceed in. Finally, I talked about how you, as a designer, can work to correct the inherent flaws of your chosen model.

A Quick Recap

The four most commonly used RPG inventory storage systems are:

  • "Rule of 99": A text-based system based around the ideal of finite numbers. Users can store a certain amount of each item—typically 99—in their inventory, but never more.
  • Weighted: Each inventory item is assigned a weighted value. Carrying more than a designated amount of weight will result in ill effects, such as fatigue or overburden.
  • Visual Grid: The inventory is represented visually on a rectangular grid. The number of grid spaces occupied by an item relates to its perceived size.
  • Realistic: Any of the aforementioned inventory systems can be used as the basis of a realistic system, as long as severe, real-world restrictions are placed upon the amount of items a player character can carry. Item scarcity is a must.

Other inventory systems exist: infinite systems and inventories that make use of supplemental storage mechanisms such as banks come to mind. But, for our purposes, the aforementioned inventory systems will offer us enough viable alternatives, especially since they can tweaked or hybridized, depending upon your design expectations.

Our four systems can be molded to fit virtually any RPG. Image courtesy of Mark Kowalsky.Our four systems can be molded to fit virtually any RPG. Image courtesy of Mark Kowalsky.Our four systems can be molded to fit virtually any RPG. Image courtesy of Mark Kowalsky.
Our four systems can be molded to fit virtually any RPG. Image courtesy of Mark Kowalsky @dimensive.

With that in mind, we posed a list of questions designed to help you get a better idea of which inventory system (or systems) would be best suited as a template for your game.  Also included were questions directly related to inventory item design and how you can differentiate your inventory system from stock templates.  We'll be using these as the basis of our current study.

Without further ado, let's take a moment to immerse ourselves in a world full of intrigue, where kingdoms fall and heroes rise: the world of Eternea, coming to a system near you in late 2014.

Echoes of Eternea Inventory Case Study

(NB. I currently work as the co-Game Designer and Project Manager for Echoes of Eternea.)

1. The Basics

We'll kick things off by asking ourselves a few general questions about the nature of Echoes of Eternea (EoE):

  1. What RPG sub-genre does your game fall under?
  2. What role will inventory play in your game?
  3. Have you designed the items that will be displayed in your inventory?
Design Tip: When designing any new system, it's best to look at the big picture first and work your way down to the minute details.

What RPG Sub-Genre Does Your Game Fall Under?

Echoes of Eternea is an RPG inspired by classics such as Lunar, Chrono Trigger, and Final Fantasy. Graphically, it draws heavily from the 16- and 32-bit RPGs of the day. The world itself is fantastical in nature, chock full of benevolent deities, ancient wizards and potent magic. In short, EoE is an old school fantasy JRPG. Based on that description alone, I was heavily inclined to implement a "Rule of 99" inventory system, akin to the one found in Final Fantasy VI.

Just because EoE is an "old-school" RPG, that doesn't mean we have to incorporate an "old school" inventory. Just because EoE is an "old-school" RPG, that doesn't mean we have to incorporate an "old school" inventory. Just because EoE is an "old-school" RPG, that doesn't mean we have to incorporate an "old school" inventory.
Just because EoE is an "old-school" RPG, that doesn't mean we have to incorporate an "old school" inventory.

What Role Will Inventory Play in Your Game?

This is a more complex question, worthy of significant analysis. First off, EoE is a fairly large game, requiring an estimated completion time of roughly thirty hours. That being said, we found the leveling curve in most 16-bit RPGs to be too drastic. While we're all about progression, part of the Hero's Journey is about overcoming seemingly insurmountable obstacles, not becoming all-powerful. Thus, we opted for a more incremental approach to leveling, marked by subtlety.

The player party would consist of nine playable characters, each of whom would only be able to equip weapons unique to their person. Armor selection would afford greater flexibility, but still adhere to certain basic principles. For instance, allowing all of our characters to equip a leather tunic was deemed an acceptable practice, but a stalwart male warrior wearing a Maiden's dress might be crossing the line.

There would be five armor slots per character, including a slot for accessories and bands.  Upgrades would be found often, but less often than what RPG fans are probably accustomed to.

Also, due to the game's flattish leveling curve, the need for multiple item tiers became less pronounced. Yet, because we decided that healing magic would be scarce, consumables would ultimately play an important role in combat.

Design Tip: Designing RPGs systems is tricky business. Why? Because a small change to one system can set off an unwanted domino effect, quickly unraveling your game's delicate balance.

Doing a bit of quick math: even if a player only upgraded their weapon three times throughout the game, that's already 36 different inventory assets. For diversity sake, we decided that there would be at least 20 variations per armor slot, three healing item tiers, and a potion that would bring a player back to life. Oh, and let's not forget that, in EoE, magic must be equipped. Assuming at least 20 magic spells, we were looking at a staggering 150+ inventory assets.

Thus, we concluded that a player's inventory should be large enough to hold a great number of individual items, but not necessarily as much as the JRPGs of old. That, and we would allow consumables to be stacked.

Implementing a visual grid started to make more sense, but only if inventory assets could frequently be sold to vendors. Still, at this point the "Rule of 99" still seemed like the way to go.

Have You Designed the Items That Will Be Displayed in Your Inventory?

At this point, no. In order to get a firmer grasp on exactly what would eventually go into our inventory, it seemed logical to tackle the monumental task of asset design next.

2. Inventory Asset Design

Asset design is a laborious task best dealt with after you have a clear idea of how you'd like your game to progress. It is highly recommended that you outline character progression first, since progression will ultimately dictate the relative power of your party's items and gear. Oh, the tangled web that is RPG design.

Luckily for us, at this point character progression had already been drafted, although admittedly in practice it would undergo several more revisions.

Either way, it was time to take on inventory assets.

  1. Which game asset types will be displayed in the inventory, and which will not?
  2. Have you fully departmentalized your inventory asset types?
  3. Have you assigned statistics to your inventory items?
  4. How readily available is each inventory asset?
  5. What's the total count of inventory assets?

Which Game Asset Types Will Be Displayed in the Inventory, and Which Will Not?

It may seem like a silly question, but certain items such as one-time use or special items don't necessarily have to appear in your inventory. Let's say, for instance, that your Hero brandishes a special amulet. It can't be unequipped, doesn't take up an armor slot, and has no real bearing on his combat prowess. Under these circumstances, is it really necessary to display it in his inventory? Hardly—although you may want to anyway, if only for lore purposes.

What if your game features unlimited ammo, or special crystals that you must deliver to the King? Displaying items that are either novelties or already assumed to be part of one's inventory can cause unnecessary clutter.

EoE incorporates several items that function more as part of the story than they do gameplay. That being said, we decided that some players might be interested in the game's lore, and thus included a special inventory tab for these items. It seemed like a suitable compromise.

Have you fully departmentalized your inventory asset types?

The next step was to break down our inventory into types. This would accomplish two purposes. First, it would allow us to more readily divide main types into further subtypes, and second, it would give us a sense of how our menu's inventory tab should be organized.

In EoE, inventory assets were first divided as follows:

  • Consumables
  • Weapons
  • Armor
  • Enchantments
  • Spells

Simple enough. Each one of our six sub-types could be subdivided further. For weapons, we decided that because each character could only wield one weapon type, weapons would be subdivided by character, and not by type. No further work was required. Armor was a different beast altogether. Case in point—armor could be divided into:

  • Helms
  • Boots
  • Body
  • Bands
  • Accessories

Helms could be further paired down into three categories: Light, Medium and Heavy. Boots and body armor followed a similar hierarchy. Bands were first broken down into elemental categories, and then grouped by tier. All told, it was a rather exhaustive, but highly beneficial process.

Have You Assigned Statistics to Your Inventory Items?

Before delegating stats, it's imperative that you determine what those stats are. Echoes of Eternea uses five core stats (Strength, Speed, Stamina, Spirit, and Defense) as a basis for a plethora of derived stats, including damage modifiers, critical hit rates, dodge %, and base hit points. While a lengthy discussion on how we designed our statistical systems is outside the scope of this article, it suffices to say that our list of core stats was kept exceedingly small for several reasons, one of which was related to inventory.

Simply stated, by using a select number of core stats, we could append the same limited number of stats to our weapons and armor. To clarify, weapons in EoE also feature Strength, Speed, Stamina, Spirit, and Defense. The added stats from weapons are then added to our characters' base stats. Done. From there we could easily calculate our derived stats, all in one shot.

Our other armor types, such as bands and accessories, would have a direct impact on our derived stats, and were calculated after the fact. The system is similar to the one that drives Diablo II: clean, efficient, and hopefully fun. It also made assigning stats to equipment a more intuitive process.

Weapon stats were kept intentionally simply. The real magic occurs behind the scenes.Weapon stats were kept intentionally simply. The real magic occurs behind the scenes.Weapon stats were kept intentionally simply. The real magic occurs behind the scenes.
Weapon stats were kept intentionally simple. The real magic occurs behind the scenes.

Item stats functioned slightly differently, as most only featured one or two components. For example, restorative potions heal a player character for a specific number of hit points, while a Phoenix Down revives a character and restores 20% of their maximum HP. In order to get the numbers right, we had to ask ourselves a few questions, such as:

  • Until what level will an item remain viable?
  • What ratio of a player's hit points should a healing item restore? Likewise, what percentage of an enemy's total health should a destructive item take away?
  • Can players use items on the Overworld?

We already determined that items would play an arguably vital role in EoE. However, we didn't want players spamming potions either (as they do in Diablo II). Instead, we agreed on a middling approach, where using items was almost always an option, but usually not the best way to spend a turn. With this middle-of-the-road paradigm in mind, assigning stats to our items became a natural process.

How Readily Available Is Each Inventory Asset?

Here's where we deviated a bit from the norm. Sometimes, vendors located in EoE's earliest areas would get their hands on powerful weapons, armor, and items. That's not to say that players would necessarily be able to afford such items, but it never made sense to us why certain vendors had access to godly gear, while others only sold low-grade trash. Also, our system would grant players a measure of choice: spend your hard-earned money on healing potions and middling gear, or go for broke and purchase a piece of gear so powerful that you may not need to rely as heavily on items. Choice is always a good thing.

That being said, inventory would be readily available, just not always accessible. Each town would have at least one vendor, and enemies would occasionally drop items and gear. The distance between safe havens would vary, generally increasing as the game progressed. This was by design, as all games should feature at least some sort of difficulty curve—Flappy Bird notwithstanding.

It should also be mentioned that, because enemies are generated on the map and repopulate slowly, then grinding, while permissible, is neither highly encouraged nor beneficial. In turn, gold would be limited enough that you couldn't go on a virtual spending spree every time you barged into town. Spend that money wisely, kids.

It's at this point where a "Rule of 99" inventory system seemed less essential, as purchasing 99 of anything outside of the most basic items would essentially wipe the player out.

What's the Total Count of Inventory Assets?

189. It turns out that our initial estimate of 150+ inventory items wasn't too far off the mark.

3. Rounding Out the Intangibles

Just a few more questions, some of which have already been answered in part:

  1. How reliant will the party be on item usage?
  2. How does the game's questing system function?
  3. Is your party composed of a single character or a collective group?

How Reliant Will the Party Be on Item Usage?

It depends, but, generally speaking, items are of tantamount importance in Echoes of Eternea. Overuse is discouraged, as your party will not have the funds to afford a nearly infinite supply of consumables. Also, players will be able to defend themselves in battle. At times, avoiding damage will be preferable to wasting consumables.

How Does Your Game's Questing System Function?

While there are few conventional quests, the game will require players to traverse large dungeons. "Rule of 99" inventories are ideal for such settings. The longer players are away from town, the more of a nuisance weighted inventories and visual grids become.

Is Your Party Comprised of a Single Character or a Collective Group?

EoE is party-based. Players control three out of a possible nine characters at any given time. While we tinkered with the idea of each character touting his or her own inventory, it ultimately would prove too confusing—sometimes you have to sacrifice a bit of realism in the name of intuitiveness.

Once again, the answer to our question reveals the "Rule of 99" inventory system to be ideal.

4. Choosing a System

Based on our findings, it appears that EoE would be best off implementing a "Rule of 99" inventory system. Although we could conceivably use a visual grid, the fact that our game is party-based would present some difficulties. In other words, it would require an awfully large grid.

The weighted system makes little sense in EoE, if only because characters need to stock up on a fair number of supplies before venturing out of town. However, what if each party member were assigned a maximum weight value? That's not a terrible idea, although I can imagine that shifting inventory items around from character to character just to redistribute weight would quickly become a unintentionally frustrating mini-game.

Finally, we reasoned that because EoE takes place in a fantastical environment, where real-world rules don't apply, it was OK for the party to carry around an exorbitant amount of items.

Given the game's party composition, sub-genre, sizable inventory, and focus on exploration, it looks like we're going with the "Rule of 99." The problem is, the "Rule of 99" system is antiquated and pretty boring. It also doesn't entirely fit, as players won't rely quite as much on items and equipment in EoE as they do in other classic RPGs. Let's see if we can mask the "Rule of 99" systems' flaws, coming up with a few creative additions of our own.

5. Making It Your Own

Now that we've chosen an inventory system, what can we do to make it our own? First, it helps to know the flaws of our current model. Luckily, we listed them in the previous segment. They are:

  • Navigating through a sea of inventory items can be laborious.
  • The system lacks a sense of realism.
  • The more a player is allowed to have of one item, the less valuable each individual item becomes.
  • Most implementations of the "Rule of 99" inventory system are visually stagnant. Walls of text may have been the accepted standard 20 years ago, but not today.

"Rule of 99" inventory systems are not exactly known for their looks. So one of the first things we wanted to do was enliven it. We accomplished this in two ways:

  • Make it more visual: In order to make our inventory menu more appealing, we used a variety of stylish fonts and shading. But that wasn't enough. After tossing around ideas for what seemed like days, we agreed that it would be best if the menu itself were semi-transparent, perched on top of our current place in the game world. That way, each time players entered the menu, they would be treated to a new "background."
  • Animate it: Animated cursors and boxes, selected items that jump off the page, and scrolling text all added life to the otherwise pedestrian task of resource management.

In order to solve, or at least reduce, potential navigational problems, we subdivided the menu into six categories: Items, Weapons, Armor, Accessories, Bands and Special. Then, we displayed items from each subdivision in two columns on the screen, reducing the need to scroll. Finally, we added an information panel, where players could read a description and view what each item does. Occasionally, we would add a funny tidbit, or a piece of lore. Plans to add additional filters, such as grouping items by type and alphabetizing them, are currently in the works.

Here's how the EoE inventory interface currently looks:

A near final version of EoE's inventory menuA near final version of EoE's inventory menuA near final version of EoE's inventory menu
A near-final version of Echoes of Eternea's inventory menu

We addressed the problem of item value by adding a synergy system to the game. Certain items and pieces of gear would have to be crafted. The component for crafting: other items. Thus, items that are either rapidly losing value or rendered obsolete suddenly have a renewed purpose. Better yet, some crafted inventory items are not sold in vendors, increasing their value further.

Unfortunately, there wasn't much we could do about the lack of realism. We changed the "Rule of 99" to the "Rule of 50," since it seemed unlikely that players would ever need, or for that matter be able to afford, more than 50 of one item. To further increase the game's sense of immersion, currently equipped gear does not show up in the group's inventory. Other than that, well... it is a fantasy game, after all.


By following a few simple guidelines we were able to identify an RPG inventory system that worked fairly well within our game's environment. We made improvements and other tweaks, with the desired effect of enhancing our audience's overall gaming experience—or, at the very least, not detracting from it.

Often overlooked and sometimes ignored, RPG inventories require the same care and attention to detail that your RPG's other mechanics do. Remember, RPGs consist of many systems, all of which must work in tandem if your game is going to have any chance of achieving success. It's undoubtedly a formidable challenge, but still way easier than fitting 99 broadswords into a pouch.


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