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I'm developing an RPG (goodness, I'm doing a lot actually.) and I'm trying to come up with a decent die roll mechanic for skills.

In d20 systems, it's usually

Die Roll + Skill + Bonuses - Penalties >= Some Target Number

For Many Warhammer (old) systems, you:

compare skill vs. skill on chart, Die Roll >= # given on chart.

For the HERO system, it's generally:

Roll 3D6 <= Skill + Bonuses - Penalties

etc.

But for each of these systems, they use a different die mechanic to determine the outcome of the action. D20 is notorious for using D8s, D10s, D12s, etc. Which you total up, and deal to someone else. That other person is then fine until they drop to 0hp. (other games are similarly designed, HERO for example using Body, STUN, and END).

Are there games that discard a second mechanic for action resolution as well as success?

For example, I'm thinking of using a black-jack mechanic.

Die Roll <= Skill + Attributes + Bonuses - Penalties

to determine if an attacker hits an opponent, and then that opponent must "resist" the damage caused by the attack, using a very similar roll. This is used on the table-top Warhammer games (Roll to-hit, Break Toughness, Armor Saves).

Damage is measured in penalties instead of in numbers. (ex. if a combatant failed 2 resists in combat, he'd suffer a -2 penalty for all other skill rolls). The penalties being easy to see/keep track of using counters etc.

  • What pitfalls am I missing?
  • What games use a mechanic similar to this?
  • What other mechanics should I be concerned about?

Thanks,


[EDIT] Thanks for all the answers. These are really great.

Damage and Death

So the game has two types of damage, Injury and Wounds.

Each Injury (IJY) over the Injury Threshold (IJT) gives the player a -1 penalty. If the number of IJY exceed the Injury Limit (IJL), they are converted wounds instead.

Each Wound (WND) over the Wound Threshold (WDT) gives the player a -4 penalty. If the number of wounds exceed the Wound Limit (WDL), they go into a coma and begin to die.

So for the complete n00b, the numbers would look something like this:

  • Injury Threshold 3
  • Injury Limit 6
  • Wound Threshold 0
  • Wound Limit 3

A mid-level cyborg might look something like this:

  • Injury Threshold 6
  • Injury Limit 12
  • Wound threshold 2
  • Wound Limit 6

Able to take far more damage, and shrug off the first few strikes in combat.

Healing will also be non-random, and if a character uses a healing item - there's no roll or chance involved. They gain the benefit, and can go on with their life.

Enemies

I like very much the mechanics in Feng Shui and in DnD 4E in regards to Minions, Monsters, and Villains. I intend for Minions to have Wound Limits of 0. (one-hit kills) while Villains would be large, hard-to-take-down mosters where tactics and cover will be your best friends.

Role-Playing Mechanics

Similar to HEX, players can spend "points" the earn during roleplaying to negate bad rolls, or improve good successes. Players are not just at the whim of their dice, but can use other resources like points tactically.

And yes, this is intended as a table-top turn-based game.

Thanks!

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as far as your penalties go, the mud dragon realms works in a vein similar to this. You get wounded on various body parts and different actions take skill penalties based on how wounded relevant locations are. This can be dangerous as in some cases once you start losing it can become difficult to make a come-back if you get hit hard enough. –  lathomas64 Nov 3 '10 at 14:19
    
My game will incorporate numerous ways of healing, and there's a party involved so someone on your team will likely be playing the role of 'medic.' The effectiveness of medicine, however, won't be subject to random effects. That's a bit too harsh, IMO. –  Stephen Furlani Nov 3 '10 at 14:22
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4 Answers

up vote 4 down vote accepted

Potential issues that come to mind:

Negative Feedback Loop

The biggest issue with degradation of skills/abilities when damaged is that you have potential for a feedback loop. The first entity to land a hit not only pushes their opponent towards death, but limits the opponents ability to respond. This makes it almost impossible for the loser at the beginning of an encounter to rally.

Asymptopic Damage Reduction

If both sides of a battle reduce their ability to hit/damage as they injure one another you may get to a point where both of them are constantly missing each other or doing such little damage that they fight to the equivalent of a standstill.

Tactical Consideration Time Available to the Player

If characters change in ability during the course of a fight the player needs the time to adjust to their changing status and react accordingly. Table top games are inherently turn based giving players plenty of time to make such considerations. If your combat resolves in real-time the effects of a degradation system can be lost of players adding confusion instead of a layer of strategic thinking.

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Excellent insight. For those reasons, I'd suggest keeping offensive capability unrelated to damage sustained, or at least making damage a sub-linear correlation, e.g. a combatant at 50% damage is 80-90% combat effective, while a combatant who's nearly dead is still 60-70% combat effective. –  Asmor Nov 3 '10 at 19:46
    
This is an excellent answer, thanks. I hadn't given thought to what happens when combat drags on... and players are reduced to less than useful. To help combat this, I was thinking of using a Wound Threshold... which I'll explain in my edit above. –  Stephen Furlani Nov 4 '10 at 11:52
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The New World of Darkness Storytelling System combines to-hit and damage in the same roll. Rolls use a pool of d10s of a size appropriate to the difficulty of the roll, and each d10 which rolls 8 or above is considered a "success" on the test. Attack rolls work like:

Attribute + Skill + Weapon Damage - target's Defense and Armor

The "successes" on that roll are equal to the number of points of damage taken by the target. There are three types of damage (bashing, lethal, and aggravated), but regardless of the type of damage, the character starts getting penalties when she has 3 or fewer "hit points" left.

This takes some feeling of agency away from the target, as she doesn't get to roll to resist getting damaged, but it makes combat a bit faster in tabletop: a single roll (single handful of dice) determines damage, and if you're repeating the attack the modifiers remain the same.

One pitfall to look out for is whether the penalties from damage will affect the target's defense. I recommend against this; it can suck when getting hurt makes it easier for you to get hurt.

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Well, exhaustion and pain should affect the defenses, even though I can see how that starts you on a slippery slope to defeatism. I'm thinking about some sort of threshold, (like an injury threshold) where you take penalties for X wounds over the threshold. I was also thinking of "stim packs" that increase this threshold to provide some 'healing' that isn't permanent but can help a character get out of a really tight jam. –  Stephen Furlani Nov 3 '10 at 17:11
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One oversight with your system; unless I'm just missing it (possible), you don't actually detail how someone is defeated. Presumably at some level of penalties, they would be considered dead/incapacitated, but you don't actually spell that out. And for that matter, such a system isn't very different from hit points. It's still a resource which combatants, which is reduced by combat, and when it hits the magic number you fall over.

Your idea reminds me a bit of Mutants & Masterminds, a d20-based (albeit heavily modified) superheroes game.

Characters and enemies don't have hit points, they have toughness. The damage dealt to them is inflicted as a DC which they must beat on a toughness save. If they make the DC, they're fine. If they fail the DC by less than 5 (I think? been a while), they take a -1 penalty to further toughness save. If they fail the DC by more than 5, they're KOd.

So there's an idea to differentiate it from HP. Instead of dying when you reach a certain threshold, if you ever fail a check by a certain amount then you drop.

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It's pretty simplistic and designed for beginner gameplay, but you might check out the combat system used by the old D&D era pencil & paper game Tunnels and Trolls.

Basically, you and your opponent get a certain number of 6 sided dice. For you how many dice you get is based on your weapon. Bigger weapons get more dice, so a great sword user rolls 6 dice and adds them up, but a quarterstaff user gets just 2. Monsters also get dice based on their level.

In addition to your weapon dice, you get modifiers (additions to the dice roll) based on your attributes. Monsters also get modifiers based on their level.

To quote from the rules...

After you get your hit point total, and your foe's hit point total, compare the two numbers. The side that had the higher number hurt the side that had the lower number. The difference between the two numbers indicates how badly the loser was hurt.

If you have armor, it just automatically blocks damage below a certain amount. Leather armor takes 6 hits for example, so if you get hit for 7 points of damage, the result is 7 - 6 or 1 point of actual damage.

Overall it is meant to be a very simple game that can be picked up very quickly and played by your average group that can scrounge up a bunch of 6 sided dice.

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I loved that game. I thought I was the only one that played it lol. –  Byron Whitlock Dec 20 '10 at 20:20
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