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View Full Version : Game mechanics design, critical success & critical failure



Mastikator
2015-01-17, 12:55 AM
The conventional game mechanic for rolling "crits" is using a D20 and letting 1 mean crit fail and 20 mean crit success. There are some variations such as using a D100 and letting 1 = fail, 100 = success, or 2d10 and 2 = fail, 20 = success. (And so on)

But I've been contemplating letting the total result determine the criticalness of the roll, for instance, if the roll is some modifier + 1d10 and the target is 15 or higher, getting 5 or lower is crit fail (even if you roll 10) and getting 25 or higher is crit success (even if you roll 1).
My main concern is this is a bit exploitable.

Has anyone any experience with a system like this? What are your thoughts?

veti
2015-01-17, 03:24 AM
Just on my gut feeling, seems like that would eliminate the big appeal of crit systems entirely - which for me, is the way they provide an outside chance (but only an outside chance) to beat the odds and achieve (or flunk) something extraordinary. Take the randomness out of it? Well, mechanically it might work, but I don't see the fun value.

Also I'd like to say that it's entirely realistic for even the greatest master to flunk a roll occasionally, and conversely for a novice to get lucky, and crit/fumble systems are about reflecting that. There is no such thing as a skill level that's too high to fail.

Frozen_Feet
2015-01-17, 03:32 AM
First thing: what do you want a critical success (or failure) to accomplish? The precursor mechanic to degrees of success was auto-hit and autofail - they existed solely to make the game fairer by ensuring no character would be completely untouchable to another. Since then, expanded degrees of success were added to make combat more "lethal" or "realistic". What they typically do, is increase swinginess of the game which might appeal to the natural gambler in us. The best (or at least most expansive) systems, like Rolemaster, make varying degrees of success into a core mechanic and use them to introduce game content. (This is also a common feature in magic systems; a big success or a big failure might lead to something completely unexpected, even game-altering, far beyond the scope and intent of the original spell.)

So yeah. Before you start crunching numbers, think on what you want. Do you want the system to be balanced? Realistic? Fun? Do you want it to be symmetric for PCs and NPCs? So on and so forth.

If the only thing it's going to do is increase damage a bit, the only effect of grading successes based on how much the exceed a target number is dramatically shortening battles where one party is already outmatched.

Beta Centauri
2015-01-17, 08:48 PM
Plenty of games have mechanics that involve better or worse success or failue depending on the degree. In Traveller, any dice roll succeeds on an 8 using 2d6, but if you roll exactly an 8 you've just barely succeeded and probably clumsily. If you roll a 12 or more (which you can do with modifiers) you've succeeded with style and maybe even gotten something extra. A 7 is a failure, but just barely, so the GM might offer a cost you can pay to pull it off. A 1 or less is catastrophic in some way. In Fate, success by 3 or more provides a bonus on a future roll, and since rolls are often opposed your enemy's success by 3 can be the result of your own poor roll. Even in D&D the exact way in which certain skills fail depends on how badly they fail.

I don't see any of these as gameable, apart from taking steps to avoid low rolls and achieve high ones. If you're worried about that, though, I recommend you talk to your players and ask them not to game that aspect of the system.

Mark Hall
2015-01-19, 11:25 AM
The conventional game mechanic for rolling "crits" is using a D20 and letting 1 mean crit fail and 20 mean crit success. There are some variations such as using a D100 and letting 1 = fail, 100 = success, or 2d10 and 2 = fail, 20 = success. (And so on)

But I've been contemplating letting the total result determine the criticalness of the roll, for instance, if the roll is some modifier + 1d10 and the target is 15 or higher, getting 5 or lower is crit fail (even if you roll 10) and getting 25 or higher is crit success (even if you roll 1).
My main concern is this is a bit exploitable.

Has anyone any experience with a system like this? What are your thoughts?

It's not QUITE out yet (I preordered, so I have the PDF of the beta), but that's somewhat how criticals in Hackmaster's GM's Guide work.

Natural 20 on a d20p means you hit. If your total is higher than the opponent's, then you critical. Your critical severity is determined by how much you beat their roll by, and how much damage you did before the critical is applied (including their armor; better armor protects against critical hits). Depending on the severity, you use a different column for the location you hit... a low severity crit to the foot might not have any extra effect, but one to the face might toss in some extra damage dice. A high severity crit can result in amputation, permanent penalties, etc.

mikeejimbo
2015-01-19, 01:19 PM
In GURPS an 18 is always a critical failure and 3 is always a critical success. However, failing by 10 or more is also a critical failure, and if you roll a 6 or under and succeed by 10 or more, it's a critical success.