The Sandbox RPG
One of the most complex and costly subtypes, and thus pretty rare -- is the sandbox RPG, which includes games like Fallout 3 and the Elder Scrolls series. Here, the player is driven by the fact that she can do what she wants, kill what she wants, be what she wants -- and do it all when she wants.
That being said, there is a bit of paradox here; in order to obtain that freedom, and be able to create her own story, the player is willing to tolerate a lot of things that she would absolutely not tolerate in any other subgenre of RPG: immersion breaking bugs, average narrative, a simple combat system, etc.
For that reason, the focus of the production and features are clearly not on the critical path, as in a Narrative RPG, but on everything surrounding it: massive numbers of secondary quests, NPCs, places to visit, dungeons to explore, etc. And almost every single feature needs to support that freedom; some of the most important ingredients of the Sandbox RPG are:
- Deep character creation, customization and evolution; remember, the player wants to be what she wants. If she decides she wants to be a thief-mage fighting with a two-handed axe, she should be able to do so (even if that might not be optimal). That's why good sandbox RPGs don't lock themselves in a rigid class system. At worst, the class system is simply a guideline for the player.
- Almost everything that the player would like to do should be doable, even if it is useless or potentially detrimental to her (like picking up brooms in Skyrim, or killing a quest giver). The player wants to do whatever she wants.
- Navigation should not feel restricted; yes, that means jumping, and no invisible walls. The player experience is freedom-based; not allowing her to jump would more or less consciously reduce that feeling massively. You will notice that almost only sandbox RPGs have a jump button -- that's the reason.
- A vast world to explore. The strength is in the details. Your world should feel alive; it should feel like it lived before and will live after the player's arrival.
- Non-linear progression. This should be obvious, but the player should feel free at all times to go where she wants, and never feel restricted by the story.
As for the ingredients that should be avoided, or be more limited, here they are:
- As with the Narrative RPG, your itemization should feel "real", so avoid a random loot generator that could give "exotic" results, for example.
- Your narration needs to find a fine line between involving the player in your world and her story, and not being too big of a focus, so that she simply follows this and loses the "freedom" experience. Skyrim did a way better job than Oblivion in this area; the developers managed this by making you feel special -- you are The Dragonborn, ensuring that you feel important to the world, and thus the world to you, without making it the only thing that matters.
- Avoid a contrasted morality system (like Paragon/Renegade in Mass Effect). The only thing it will achieve is to make the player feel like she should follow one path over the other, and thus decrease the feeling of freedom.
Freedom is your keyword; never forget it.
The Dungeon Crawler
That subtype is one of the most easily recognizable; games like Torchlight, Dungeon Siege, Diablo, and even Dark Souls are part of it. Once upon a time they were clearly defined as "hack 'n slash," but recently they joined the ever-growing group of RPGs called "action RPGs" (this is an issue; more on this later.)
The main thing driving the player here is, by far, character progression (through statistics, new abilities, or loot). Evolving your character from level 1 to, well, a lot, finding always more powerful loot, acquiring more and more powerful powers -- to kill stronger monsters that will drop better loot, and so on.
They trace their roots in your typical old school Dungeons & Dragons game, where the plot was simply a pretext and context to kill monsters and loot their stuff. Decent graphics and immersion is expected, but above all, the main focus of the production and features should be: loot, combat, a statistics system, an evolution system, a class system, etc. Anything that can make the evolution of the character more thrilling and granular should be considered a priority.
Some essential ingredients to focus on:
- Complex loot system. Your random loot generator will be generating most of your "breadcrumbs" (more on this later); it should be your top priority.
- Customizing this loot is also important -- slots for runes, gems, enchanting, and those kinds of things are always nice to have.
- Deep character evolution. A class system, stats system, skills, feats. That's the main reason the player is playing; don't let him down.
- Deep and detailed lore and universe -- that's your context, not your narrative itself. Having interesting lore, remarkable characters (who doesn't know Deckard Cain or Tyrael?), and varied environments will go a long way into creating a comfortable place for your player to grind through all those monsters.
- Your enemies must respawn, even the bosses! That's critical. Your player will want to keep farming those guys for more loot, experience points, runes, gold, or whatever. That's the whole point of the thing, and while it is detrimental to a narrative RPG, it is completely mandatory for a good dungeon crawler. Do you think Diablo would be as fun if you couldn't farm the hell (literally!) out of Diablo himself?
A few things to avoid, in my opinion:
- Narrative is secondary, and could actually hinder your main experience if it's too present. Typically, you should avoid complex dialog systems with multiple choices; while they are a must in a narrative RPG, they are just a loss of time for most players playing a Dungeon Crawler; they want to kill, bash, loot, level up -- not make complex morality choices or define their character's personality. They are also not looking to be emotionally engaged by the story.
- Avoid open worlds; for some reason, that's something that a lot of hack 'n slash games tried, and it never worked very well. Sacred is an example. The main reason is most certainly that the player doesn't want to lose time running around, and also wants to have an easy way to simply restart a dungeon in order to go farm that boss again and again. I know it sounds cool to say "We have an open world hack 'n slash", but in reality, the only thing it will do is make you lose a massive amount of time and resources production-wise, and dilute the main foci of your game: character evolution. In any case, you will never be a Skyrim or Fallout, so you will never satisfy the players looking for freedom. Trust me -- don't do it.
Character Progression is your keyword; never forget it.