Sunday, March 8, 2009

Combat Mechanics for Modified GURPS

Continuing from yesterday-- a summary of Combat Mechanics. Gene has me looking at BESM 3e, so I have to go through that as well. Basically I'm trying to work through how thinly I can slice the rules and still have it taste good. This is another game mechanics post, so if that's not your bag, feel free to skip.

Combat will be a simplified version of the Gurps combat system. We're leaving off a lot of the most crunchy bit and focusing on play and strategic choices.

On your turn you get a MOVE action plus another action. Your MOVE is equal is the number of yards you can cross in an action. Armor and Equipment may slow you down. Your second action may be one of the following:


Additionally, it is assumed you can do small actions freely on your turn: looking around, drawing a weapon, shouting orders and so on. The GM may allow players to forgo their MOVE in order to do something a little more complex and still take their normal action-- this might include doing a full survey of the battle to assess things, kicking an obstacle into place, finding something specific in your bag and so on.

To make an attack you have to be in range. To make an attack with a ready weapon, you roll 2d10 and try to roll equal to or under your skill with that weapon. Circumstances and situation may modify your attack roll. If you roll under the modified number, you hit the target.

If a target is aware of the attack, they may try to defend. On each round a character may make one Parry, one Block (if they have a shield) and unlimited Dodges. A character's Parry is equal to (one-half their weapon skill) +5. Ranged attacks may not be parried without a special talent. Light weapons trying to parry enormous weapons get a penalty. A bare-handed character may only parry bare-handed attacks unless they have a special talent. Block is equal to (one-half their melee skill) +5. Some shields give bonuses. Dodges are equal to (Basic Speed) +5. Some area effect attacks give a penalty to dodges.

You can only make one defense roll against any attack. You usually only get one Parry and one Block per round.

If you hit and the target does not defend, you roll damage (see later).

To make a Feint you make a contested roll of your Weapon Skill versus the opponent's weapon skill. If your Bluff is higher, you may use that for performing a Feint. If a person's Sense Motive is higher than their weapon skill, they may use that for resisting a Feint.

If you win the contest, the margin of victory is subtracted from the target's active defense rolls against you until after your next action. You may declare your Feint as affecting another person also engaged in combat with the target-- handing the defense penalty to that person's attacks against the target.

All-Out Attack
If you choose to make an All-Out attack, you lose your active defense until your next action. You may make a Defense roll against attacks you are aware of, but you have to roll a 5 or less. This number is not modified by any other abilities (with some exceptions). You may only make an All-Out attack with a melee/HTH attack.

An All-Out Attack maneuver allows you to:
*Make two attacks against the same target or one attack each against two targets within reach.
*Make one attack at +5 to hit.
*Make one attack at +3 damage
*Make a Feint immediately followed by an Attack
*Move twice and then attack.

If you are using a ranged weapon, you may Aim to give yourself a +5 to hit on the following attack.

If you take a Full-Defense you may either:
*Add +3 to your Defense roll of one type (Parry, Dodge, Block) until your next action.
*Roll two different Defense rolls against attacks until your next action. Remember, you usually only get one Parry and one Block per round.

Move a number of yards/spaces equal to your Move value. Move is usually based on your Basic Speed, modified for armor and encumbrance. Standing up after being knocked down is a move action, unless you make an Acrobatics check.

Non-ritual spells require one action to Prepare and one action to Cast. If a caster has applied the Fast modifier to their spell, Prep and Casting can be done in a single action.

Where a caster is controlling something at a distance or something of the sort, the GM may require them to spend their action Concentrating. If they are struck while Concentrating, the GM may require them to make a WILL check to remain focused.

Complex Action
This is essentially any non-attack action which might require a skill test to perform.

Long Action
Anything that requires multiple rounds to pull off-- like reading a book or rebuilding a broken device.

Characters have a base damage they deal based on their Strength (ST) stat. This base damage comes in two forms-- Thrust (TH) and Swing (SW). Weapons do damage in various types, usually with a bonus listed to the character's base damage. None of this is actually complicated in play, since you'll record your damage on your character sheet.

As an example of damage, Scott has an ST of 13-- that means his base damage is 1d6 for TH and 2d6-1 for SW. He's using a Thrusting Broadsword-- it does TH+2 Impaling damage or SW+1 Cutting damage. So he'd roll 1d6+2 for a thrust attack or 2d6 for a cutting attack. Keep in mind with damage, when you get to +3 in bonuses, you jump up to the next die -1.

Basically, there's three kinds of damage-- measured by how much extra damage it does after Armor. A Crushing attack does straight damage, a Cutting attack does +50% damage, and an Impaling attack does double damage. Again, this is relatively easy to calculate on the fly. Armor has Damage Resistance (DR) which is directly subtracted from the damage.

As an example, let's say Scott's hitting a guy with Heavy Leather armor, DR 3. If he does a thrust attack, he rolls 1d6+2...let's say he rolls a 3 for a total of 5. That means two points gets through, which is then doubled so the target takes four points. If Scott had been Swinging he would have rolled 2d6...let's say he rolled 7-- less the 3 DR means 4 gets through, which becomes 6 after we add the +50%. Again, the GM's used to these calculations and can do them very quickly.

Damage is subtracted from your HP. On the round after you've been hit, you have a penalty equal to the damage you took. This applies to Attacks, Casting and Concentration but not Defense rolls. If you take more than half your HP in a hit, you have to make a Health (HT) check to avoid being Stunned. When you hit 0 HP you have to make a HT check to stay up-- when you reach below 0 HP you have to make HT tests each round or whenever you get hit to take an action, additionally, you have a Move of 1. You start making Death Tests when you get to -(Health) in HP.

This is always a wonky set of rules in any game system. You roll to hit using HTH skill-- and then roll a Quick Contest of ST or DX (choice) versus ST or DX. Certain combat styles can give bonuses elements. If you keep your hold, then the target has their mobility and actions reduced. They can make another attempt to escape (another Contest) on their round.

If you keep a hold on someone, on the following round you can attempt to cause damage, attempt to bear the person down to increase the hold, or even throw the person. This requires a skill check. It is possible to grab and throw someone on the same action, but that requires an All-Out Attack action.

Hit Location
You can try to hit a specific location with an attack. Each location has a different penalty to hit. You can do extra damage depending on the area you hit. Called shots are all or nothing. Limbs can be disabled.

Criticals and Fumbles
You get a Critical Hit if you roll a 2 or a 3. If your skill is 14+, you Critical on a 4-. If your skill is a 16+, you Critical on a 5-. If your skill is a 18+, you Critical on a 6-. You can only defend against a Critical Hit by rolling a Critical Defense.

A Critical Hit allows you to make a roll on the Critical Hit table for additional effects. They're usually pretty cool.

A roll of a 19 or 20 is a Fumble. You can injure yourself...badly.

To disarm, you make a standard attack, with a penalty for trying to hit the weapon (-4 to -6) depending on the size of the weapon. If you hit and the target does not defend, you make a Quick contest of Weapon Skill versus Weapon Skill. If the target loses, their weapon flies a yard away.


  1. I dunno. I am spoiled now with your card system. It is so easy, as well as being open-ended and more creative.

  2. Absolutely-- and I think for some kinds of things the card system is the best way to go. For anything focused around narrative and story primarily, I'll go with the cards. For example I'd do Firefly, any kind of investigation game, Mage, or the like with the card system.

    If I want a little more crunch though, ala old school Dungeon Crawls, High Fantasy and so on, I think the cards system works less well-- or rather I could modify it to simulate that but I think I'd lose some of what makes the system work.

    But yes, I really like the Card system- especially since it is so easy to run for and puts more power in the hands of the players.

  3. I'd love to read comments from the people who love Rolemaster crunch, and how they'd like to see a modern version of it. I tend towards simplicity.

    Specific to this post, I'm not a fan of GURPS attack/defense rules. If I have Mace skill level 18 and roll a 5, I hit but haven't scored a crit. If the defender has Block 12 and rolls a 12, he's warded off any attack except a critical hit. This means that even a high skill character will repeatedly fail to hit a high defense character. There's no melee solution for this problem.

    BESM's solution is to make combat a contested roll. You compare the total of attack and defense rolls, plus skills and modifiers. Whoever has the highest total wins. Most systems have an attacker roll against the defender's fixed defense target number, which is simpler still.

    GURPS is bad for contested rolls because you need to calculate a negative number (skill 18, roll 12, -6 margin) which you then multiply by -1. This gets especially difficult if your effective roll is negative (skill 18, roll of 6 with +8 to hit, effective roll of -2, -20 margin).

  4. I like it; just enough crunch. Nice work.

  5. >>GURPS is bad for contested rolls because you need to calculate a negative number (skill 18, roll 12, -6 margin) which you then multiply by -1. This gets especially difficult if your effective roll is negative (skill 18, roll of 6 with +8 to hit, effective roll of -2, -20 margin).<<

    Gene, I'm stunned. You're making it waaaay more complicated than it really is. There's no need at all to throw so much math into it (i.e. multiplying by -1 and such).

    If you have a skill of 18 and you roll a 12 then you make the roll by 6. That's it; no math other than what is required to determine if you make a roll or miss it and by how much in either case. Same goes for your second example: if you have a skill of 18 and have +8 to hit then your effective skill is 26. Roll a 6 and you make it by 20.

    For contested rolls, whomever makes their roll by the larger amount is the winner. GURPS is only bad for contested rolls if you make it that way by over complicating it with unnecessary mathematics.

  6. I'm not saying GURPS math is hard. It's harder than simple roll high + mod contested rolls. The prefrontal cortex has very little RAM, so it's bad for a game system to distract it. Addition tends to be fast, switching between addition and subtraction tends to slow things down.

    I've repeatedly seen people go through the "Made it by six! No, seven!" at the table. People like chemists and engineers. It slows down play. People who aren't professional math users (like me and most folks) have to do their sums out loud when they switch targets and modifiers. We often skip the "No, seven!" part or delay it until we catch it later. "Damn, Rob, my math was wrong last turn. I didn't miss by one. I hit!" I've only done that once, but it was annoying. Rob K was gracious, and gave me the hit retroactively. I didn't think I deserved it, but I didn't argue the point.

    Even incremental simplification can really speed up a game and improve play. Lowell is going to try to avoid "margin of success" rules in his GURPS, which is good.

  7. Sure, GURPS math is harder than a simple roll + mod, but that's like saying "2" is higher than "1". It's true, but it's such a small difference that it's not an issue.

    I agree that any amount of simplification is good for a game, but you're still shaping GURPS math into something over complicated. 99.9% of the rolls you make require nothing more than checking whether you make your skill roll or you don't. Which is exactly what you mentioned earlier when you said "Most systems have an attacker roll against the defender's fixed defense target number, which is simpler still". The fixed defense target number in GURPS is your skill number. Simple, no?

    Going back to contested rolls, in the many years of playing/running GURPS I could probably count the number of contested rolls I've seen on two hands, and none of them took any more time to accomplish than a normal roll. The system just doesn't require them very often.