A lot of players seem to like rules-heavy–or “crunchy”–game systems. They seem to think they provide flexibility and realism (or at least verisimilitude, particularly over rules-light systems where the GM just decides how things go. But do they really? And is there a sensible alternative?

The Difference

As an example, let’s imagine you want to answer the question “Can my character jump over this chasm?”

In a rules-light system, you might write that the GM created the chasm, so he can simply decide which characters, if any, are able to jump it. Maybe humans and elves can, but dwarves and halflings are too short.

In a rules-heavy system, you might write that the formula for a broad jump with a running start of at least 10 feet is your height plus your strength bonus, plus 1d3, times 2, in feet. So if you’re 6 feet tall with a +2 and roll 2, you can leap 20 feet, but if you’re 3.5 feet tall with a +0 and roll 1, you can leap 8 feet. Now all the GM has to do is ask the players how far they can jump (and help them with the calculation) and then figure out how narrow the narrowest part of the chasm is. “But wait! My character has the special jumping feat!”

In the first case, consistency is a problem. And some players may disagree that halflings can’t jump very far. “The description even says they’re adept at running and jumping!”

In the second case, time and effort are problems. Does the GM even know exactly how wide the chasm is at its narrowest? And it takes a lot of effort to read and interpret the rule, then apply it, and then what have you accomplished? The human and elf jump the chasm, but the dwarf and halfling can’t.

But notice how you have to specify things like “a running start of at least 10 feet” and similar conditions. And when you specify a condition like that, you immediately create the need for a standing broad jump rule of similar complexity, where the character can’t get a running start. Such rules proliferate to fill volumes, particularly because it becomes very tempting to create auxiliary rules, like the special jumping feat and exceptions like “unless the character is moderately to heavily encumbered” and such. Then you need even more rules for when characters are encumbered.

Similarly, if you create a rule for resting, you might say characters regain all their hit points by resting overnight in a safe place, like an inn. But then you need a rule for sleeping rough, say up to half your hit points. But then… it’s very tempting to create more rules about how rangers, druids, and/or barbarians get all their hit points back even when sleeping rough… And now you’ve got three or four rules instead of one. Worse, it’s a rule with an exception, with a sub-exception to the exception.

Skill Checks Solve the Problem

The middle ground is wide, tho. A sensible rule might be that the GM created the chasm and so sets a difficulty for leaping it. Then humans and elves get +4, dwarves get +1, and halflings get 0. Then the leap is a skill check. If there are extenuating circumstances, such as being encumbered, the GM applies a penalty on the fly.

Using skill and ability checks this way can resolve a lot of issues that would otherwise require complex rules with different mechanisms. But when you define just a single mechanism, you can afford to have a few suggestions for bonuses and penalties that apply to special situations, so the GM doesn’t have to decide on the fly.

This creates consistency and confidence in the GM and players. Everyone knows they’ll have to make a skill/ability check, and they know how to do that, so they just need the difficulty number and an idea of what could give them a modifier.

Now, turning every question into a d20 check could get dull. Combat being prevalent and requiring various die rolls helps to avoid that, but certain other rolls using different dice are good too. A d6 roll here, a d100 roll there… Use these for determining the number of things involved (you break 1d6 arrows in the fall), a choice on a d100 table, etc. rather than checks. Then d20 checks are specifically for determine the success or failure of an attempt that uses a skill or ability.