I've been playing a lot of Shadowrun (5th edition) and Imperium Maledictum and Call of Cthulhu lately, because some folks I play with seem to enjoy investigative adventures. I was discussing this with my partner (who herself is one of the players who generally prefers investigation and to combat) and she asked whether there were investigative adventures for D&D. My automatic response was that there were, because of course you can literally do anything in any RPG, but I hadn't found that many that appealed to me. But the more I thought about this, I had to admit that even an adventure like Rise of the Runelords didn't exactly "feel" the same as a game designed for investigative storytelling. Which made me wonder: What about the design of a game makes it appropriate for either combat or investigation?
Some roleplaying games make it obvious what exactly they're meant to be about. It's often the text on the back of the rulebook. Here are two examples:
Shadowrun: You are a shadowrunner, thriving in the margins, doing the jobs no one else can. You have no office, no permanent home, no background to check. You are whatever you make yourself. Will you seek justice? Sow seeds of chaos? Sell out to the highest bidder?...It’ll cost you something—everything does—but you can make it worth the price.
Starfinder: Blast off into a galaxy of adventure!... Step into your powered armor and grab your magic-infused rifle as you investigate the mysteries of a weird universe with your bold starship crew.
These are arguably two similar games, in many ways. They're both sci fi with magic, but Starfinder reads like an homage to Starship Troopers or Star Trek, while Shadowrun suggests Peter Gunn or maybe Raymond Chandler. These two systems are flexible enough to swap their descriptions around. I've run a Shadowrun-style adventure within Starfinder, and I've run combat-heavy adventures in Shadowrun. But if we're asking for the intent of the game system, it's in the description.
Ideally, the description on the back of the rulebook matches the mechanics you find inside the book. Right or wrong, consciously or subconsciously, most players interpret what they're "allowed" to do in an RPG based on what they can roll dice for. We're all secretly playing chess, except the chess pieces are our character's abilities. If the rulebook says I can use my skill of History or Lore as a way to gain insight about a suspicious object at a market, then it's more likely that I'll investigate objects at the market rather than, say, haggle over its price. But if a skill allows me to negotiate for the price of an object at the market, then I'm more likely to haggle than scrutinize. That's not to say that a player couldn't do one or the other just by proposing it to the game master, but the power of suggestion is strong, and I think there's also comfort in following the written rule.
Taken as a group, the attributes and skills provided a character in a game communicates much to a player. After spending an hour or more building a character that's all athletics and armour and fighting stances, you expect to use those attributes in the game. Otherwise, why give you those options in the first place?
Many players also have at least a latent sense for which rules provide a satisfactory level of detail and precision. If computer intrusion comes down to a single roll determining failure or success, then the game system probably isn't actually about hacking. We all assume digital intrusion is pretty delicate work, so we expect complexity when attempting it in game. Maybe there's a roll to scope out the network, another roll to gain access to a specific system, and then a roll to escalate privileges, and so on. One system design betrays a certain interest in how to express interactions with computers, while the other makes all computers into toasters and tests you on whether you can successfully fit the bread in the slots.
There were several series of tests my players had to perform in a recent Shadowrun game that I don't believe could have been replicated in a standard fantasy system like Tales of the Valiant or Pathfinder. Sure, in a fantasy game I could have the players roll a series of dice just using base attribute modifiers, but the aspects of the player characters being test wouldn't have been narratively developed, and there would be few mechanical benefits to help the player character succeed. It would be like flipping a coin. There'd be no illusion of agency or advantage. It's just not the same experience.
Like the description back of the rulebook, most games accentuate a certain theme, and evoke familiar tropes. You can ignore these and just use the mechanics of the rules, but it usually feels like you're going against the grain. I think this is down to two factors.
First of all, you didn't buy a recipe for game play, you bought a game. When most of us buy a game book, we're buying the idea of the game first and foremost. Many (if not most) avid roleplayers have books for systems they'll never play, or that they'll only play once or twice.
We buy game books based on the cover art, the intrigue of the game's mechanics, and the lore of the setting. We generally don't want to use the rules of a game about occult investigation for an adventure about delving into dungeons for gold. If we want one, we buy the book for it, and if we want the other then we buy the book for that.
Secondly, game mechanics are usually flavoured for the game you're "supposed" to play. Names of spells and descriptions of weapons and skills spark our imagination, but also have an internal logic. It's easy to narratively re-skin a Ray of Frost spell as a Deathly Fairy Sparkles spell, and yet it rarely feels quite right until it's written down as a rule. We want to be told about the magic that exists in a setting. We don't want to have to sew our own costume and throw it onto a spell at the last minute.
Besides that, you can't logically re-skin everything. A crossbow is a crossbow. A pistol is a pistol. A lasgun is a lasgun. They share a lot in common, but they should each have distinct nuance. You can plug the same numbers from one to the other, but it would be weird for a pistol to only shoot once before requiring a reload, or for a lasgun to do no heat damage, or for a crossbow to have a magazine. We like our distinctive arrays of numbers and words, and we like for them to relate to the larger fictional world they live in.
I love a good universal system, and I enjoy abusing systems to make them universal. And while it's always a fun experiment to see how far a rule system can be stretched, I have to admit that it has demonstrated two contradictory truths about RPG and wargame rules.
If we all truly wanted a catch-all system, then most game books would be written as generic game systems. They aren't, and that betrays much about what we actually enjoy about the gaming experience.