I love playing RPGs and dreaming up stories and scenarios ... but when it comes to creating a system, I just suck. :(

After looking at most systems, I decided that I want something simple.

What sort of system (formulas) would you use for combat resolution based on the following stats:

Attack (Physical Attack)
Defense (Physical Defense)
Intelligence (Magic Attack)
Resistance (Magic Defense)

Also, characters have weapon skills that are ranked as follows: F, D, C, B, A, and S. So that should modify the Attack skill.

I was thinking of something like ( Attack ) / ( Attack + Defense ). So for example, if player has an Attack of 50 and a monster has 50 Defense, he would have 50% chance of attack. Does that sound right?

What do you guys think? Any suggestions will be very very welcomed!

Hi!
  I think instead of making a forumla, try this (Its even simpler):
  Attacker rolls under their skill on dice to hit
  If Defender rolls under their skill, they turn a hit to a miss.

  There is a formula to figure out how this bowls down to actual hit probability:
Attack% * x (100-Defend%)
  So, in your example the attacker has a 25% chance to hit.

Welcome to the forge,

Here's a few lateral thoughts: Are you looking for a system that gets the player excited about the result?

I'd suggest that the system wont get a player excited. It's like the player was betting $1 in a really complicated and interesting dice roll system. But regardless of how interesting that system is, it was still just a $1 bet. While someone betting $500 on a simple coin flip...well, that coin flip sounds moronically simple and how could that be interesting? Well, when it's $500, it's interesting.

So the first step may be to ensure what the players are putting at risk is significant. When it's significant, whatever system you do end up using, will look all the better for it.

I really don't think formulas are the way to go. Not if you want something simple. For me, math really slows down a game. Simple addition is usually OK. Subtraction gets harder. Division--well, I probably just wouldn't play.

If you're designing a system, I'd start by looking at what other people have done:

• You could use dice pools or roll a single die.
• Your stats could determine the number of dice to roll, determine the target number, or simply add to the roll.
• Players could roll against a target number--or they could compare their results to an opposing roll.
• The results could be determined based on the results of a single roll, or you could have a cascading number of rolls (I make an attack roll, he makes a defense roll, I make a damage roll, he makes an armor roll...).
• You could resolve the entire scene with a single roll, or roll for each strike and counter-strike.
• Rolls could be based entirely on information on the character sheet--or there could be considerable amount of information traded between the player and the GM before a roll can be made.
• How much random variation is there in the rolls: too much and payers will become frustrated when experts fail at relatively simple actions, too little, and why bother rolling at all.
• ...and so on...

Pick elements you like the most and use them as the core of your system. Think about why you enjoy those elements, what makes them appeal to you. Do you like the challenge of resource management? Do you want a light system that stays largely invisible? Once you know the type of game you want to play, try and make every part of the system support that style of game.

I rarely find myself excited by a game's mechanics--but bad mechanics can definitely ruin an otherwise good game.

I hope that helps,

-Rich-

Sounds like you have something based on BRP (Basic Role-Playing), the system behind such luminaries as Call of Cthulhu, old RuneQuest, Elric!, etc.  BRP used a table, with mathematical progression as I recall, where two people would compare a stat or a skill and look on a table.  A 20 vs. 20 would be 50%, a 10 vs. 20 would be 25%, etc.

The exact formula would depend on graininess, and what kind of scaling you want to use for higher and lower stats.  That is, if you have a stat progression of 1-100, that's a lot grainier than 3-18.  3-18 might use a 5% scale -- if 20 vs. 20 is a 50% chance of success, then 19 vs. 20 might be 45%.

Another formula to use if you're comparing percentages is Attacker minus Defender + 50.  Thus, the same number vs. the same number would be 50%, modified up or down by 1% per 1%.  Thus, a 54 v.s. a 50 would yield a 54% chance.

You could also use something similar to the Lone Wolf gamebooks.  From Everything2.com:

"To see how much damage you do in combat, you look up the appropriate combat skill difference and random number you received earlier in the Combat Results Table. The damage received by both you and the NPC will be displayed. For example, if you (Lone Wolf) have a Combat Skill of 25, and your opponent has a Combat Skill of 13 (a difference of 12), and you receive a random number of 9, you will score an instant kill and receive no damage. Another example: you have a Combat Skill of 25 and your opponent has a Combat Skill of 30. You roll a three. You receive five damage and the enemy receives two."

A table can be found here: http://www.geocities.com/iainsmith/01-HH/crtneg.gif and another one here: http://www.ncf.carleton.ca/~as300/excrt.html.  E = Enemy and LW = LW. 

I personally use Risus.  It's free, it's simple, it's independent and there's lots of web support.  People just describe their actions in plain English, and whoever rolls higher wins.  Armor modifies damage received, and Weapons don't really figure in that much at all, unless you're doing something clever with them.  It lets Legolas with light armor and twin daggers and Bors (from the film King Arthur) with (again) light armor and daggers actually *do* something instead of doing wimpy damage and standing around waiting to get killed, as would happen in the big three (HERO, GURPS, D20).

I'm working on a matrix for combat, based on Attack High v.s. Duck, or Right Slash v.s. Block Middle, that sort of thing.  One Attack Maneuver vs. one Defense Maneuver modifies the damage done.  No rolling to hit.  Why have a Combat Skill?  To tell what maneuver your foe is using and choosing the best option to counter it, and it figures directly into damage.

DeviantBoi wrote:
I love playing RPGs and dreaming up stories and scenarios ... but when it comes to creating a system, I just suck. :(

After looking at most systems, I decided that I want something simple.

What sort of system (formulas) would you use for combat resolution based on the following stats:

Attack (Physical Attack)
Defense (Physical Defense)
Intelligence (Magic Attack)
Resistance (Magic Defense)

Also, characters have weapon skills that are ranked as follows: F, D, C, B, A, and S. So that should modify the Attack skill.

I was thinking of something like ( Attack ) / ( Attack + Defense ). So for example, if player has an Attack of 50 and a monster has 50 Defense, he would have 50% chance of attack. Does that sound right?

What do you guys think? Any suggestions will be very very welcomed!

Goal:  Be under goal number after all bonuses and penalties

Bubba 1 Attacks Bubba 2

Goal Number = Bubba 1's Attack (or Intelligence) + Bonuses to Bubba 1 + Penalties to Bubba 2's
Attack Proficiency = Bubba 1's D100 roll + Bubba 2's Defense (or Resistance) + Penalties to Bubba 1 + Bonuses to Bubba 2

IF Goal Number > Attack Proficiency:
    Success
ELSE:
    Fail

About as simple and straight foward as I can get it.  A derivitive of what has been said.  Modified so the only thing you do is add and compare which is bigger.  Change dice roll to preference.  You can ignore bonuses and penalties where needed.

DeviantBoi (and, gee, I feel kinda funny calling you that... do you mind us using your real name? I'm Sydney):

Everybody's had useful suggestions here, but we really can't help you unless we know what you're trying to achieve with this combat system besides "simple." There's are some very different, very good combat systems out there, each designed for a specific purpose -- historical accuracy and complex tactics in The Riddle of Steel, balls-to-the-wall drama in The Shadow of Yesterday (which actually uses the same rules for seducing someone as running them through with a sword), slow-burn escalation in the Western game Dogs in the Vineyard and its horror spin-off Afraid. I'd strongly suggest you take a look at a couple of these, as they're all pretty different from either GURPS/Champions, BRP, or D20/D&D.

What do you want combat to feel like in your game? In particular, think about whether the psychological aspects of combat matter to your game -- should the big, strong, fast guy with the big weapon always win, or should the sneaky, smart guy be able to get the drop on him by surprise, or should the little guy with a sharp rock and fire in his eyes be able to prevail by sheer force of passion? I'd check on this thread that I started to canvass people's ideas on this subject at http://www.indie-rpgs.com/forum/index.php?topic=10977.msg116720#msg116720

What Sydney said. Until you have your design goals known, talking about formulas is useless.

Just to put things in some perspective, in fact, you get my #3 Rant.

Mike

Hi, thanks for the comments. My name is Jesse, by the way. :)

I'm trying to build a game similar to Kingdom of Loathing (http://www.kingdomofloathing.com).

Like I said, I've seen many RPGs and the problem I run into is that their stats usually only reach 20 or some other low number. It doesn't allow for unlimited stat growth (which is important to keep people progressing in the game, setting no limit, and making them get stronger and stronger).

Let's say you have an Attack of 300 and your opponent has a Defense of 50. You roll a 20 for Attack and the monster rolls a 21. It doesn't seem fair that a monster with such low defense gets to block an attack from a powerful character. So rolling and comparing numbers doesn't really work. But in the other case I described above, you would get 300 / (300 + 50) = 85% of hitting. Sounds better, but not quite. Maybe if your attack skill is twice as much or more than the opponent's defense skill, you get an automatic hit. (Anything less than 150, in the case here, is an automatic hit).

So, once you figure out your percentage to hit, you would roll a d100. In case of 85%, you would have to roll a number between 15 and 100 to land a hit. However, the weapon skills (F,D,C,B,A,S) affect the roll you take. You would only be able to roll the following numbers:

Weapon Skill F: 0 to 25
Weapon Skill D: 0 to 50
Weapon Skill C: 0 to 75
Weapon Skill B 25 to 100
Weapon Skill A 50 to 100
Weapon Skill S 75 to 100

So, someone with an F skill can still hit the opponent in the example above (1-15 misses, 16-100 hits), but it wouldn't really be 85% chance of hitting cause he would only roll 0-25 ... more like 40% (if my math is correct).

So, is there something out there that is similar to what I'm trying to do. I know that all of Nippon Ichi's RPGs on the PS2 have systems that are similar (too bad I have not found any formulas for them).

I appreciate the help!

Jesse.

Bit OT but I'd really like to see more of this system as you develop it.
It something I've been working, getting a game combat system that reflects my experience of actual combat styles, with a playable and workable game mechanic.
HW

steelcaress wrote:

I'm working on a matrix for combat, based on Attack High v.s. Duck, or Right Slash v.s. Block Middle, that sort of thing.  One Attack Maneuver vs. one Defense Maneuver modifies the damage done.  No rolling to hit.  Why have a Combat Skill?  To tell what maneuver your foe is using and choosing the best option to counter it, and it figures directly into damage.

Not really and answer to your point but combat is really about Action/reaction, not attack/defend, if you defend you lose! Rather if you wait for your opponent to act and then try to exploit that.

Hereward

DeviantBoi wrote: Like I said, I've seen many RPGs and the problem I run into is that their stats usually only reach 20 or some other low number. It doesn't allow for unlimited stat growth (which is important to keep people progressing in the game, setting no limit, and making them get stronger and stronger).

There are many good comments here and I would like to just chime in and second a few of the ideas mentioned.  I think you are heading in the right direction, but I would not worry too much about the combat resolution at this time.  You say you want a math lite type of system.  Then what IS important in the system?  Focus on that. 

If you want combat lite and have great gameplay you could resolve conflict with a coin toss.  That is about as simple as it gets. If everything else rocks your players won't mind flipping a coin to see who "wins" a combat.  Point is, the math is not important if that is not your goal.  If your goal is to make a system based on realistics fight dynamics be prepared for lots of math.

I'll chime in here with one of my personal design philosophies:

If your system is not simulationist-accurate to a 1% level and/or character actions are not really important at a 1% level, then percentile dice are kind of pointless. The same point applies if you roll percentile dice but all modifiers are in 5% increments (might as well just roll 1d20!). If you're using percentile dice because you have so many neat ideas for combat that require some sort of hierarchic sorting, such that percentile dice are the only way to fit them all in...then you have too many combat rules.

That said, I'll be a heretic and disagree with Mike's standard rant #3. I think any situation where a player's action/reaction/inaction can end up getting their character killed should have some extra game mechanism to make sure that a gameworld-appropriate (important!) level of risk, reward and GM impartiality is applied. In most rpgs, combat is that situation. Which is why we have games with oodles of combat rules (often too many, tis true), and not nearly as many landscape photography rules.

Greg Porter

wrote: Like I said, I've seen many RPGs and the problem I run into is that their stats usually only reach 20 or some other low number. It doesn't allow for unlimited stat growth (which is important to keep people progressing in the game, setting no limit, and making them get stronger and stronger).

1a: The protagonists fight monsters of increasing scale until they get the bad guy at the end.

2a: The players cooperate against the GM to defeat the adventure that's been planned out.
2b: The players compete with each other to get the most and best monsters.

1b: The protagonists are politicians in a court environment where a cutting remark can kill as well as a stiletto.

2c: The players build a conspiracy theory chart out of premade cards and tell stories for each card they add.
2d: The players build alliances between their protagonists and NPCs and use them against each others' interests.