Stats relevant to combat in G&G are:
- Armor Class, which is ascending from a base of 10
- Hit points, which are pretty much what they've always been.
- Combat Rating (aka Attack Bonus or some such) which is determined by character class and level or monster Hit Dice.
- Damage: How much harm a weapon or natural attack routine can inflict. May be expressed simply as a maximum (e.g. "4") or as a dice range (e.g. "1d4," if you use an optional critical hit rule.)
The core combat mechanic is a d20 roll, which has been referred to as the "to hit roll" or "attack roll" in most games, but which I'm calling a "combat roll" to call attention to the fact that it does not necessarily represent a single attempt to hit an opponent. Likewise, I prefer to think of successful or unsuccessful combat rolls rather than "hits and misses."
In the most basic form of combat, a combatant makes a d20 combat roll against its opponent's armor class to determine if it successfully inflicts damage. Combat Rating and adjustments from ability scores and magic, if applicable, are added to the roll. If the total exceeds the opponent's AC, damage caused is equal to the difference between the adjusted combat roll and AC. So, if a fighter engages a creature with AC14 and scores a total of 17 on her combat roll, she does 3 points of damage to the opponent.
The Damage stat is a cap on the maximum damage possible, so if our hypothetical fighter is using a Damage 4 weapon and beats her opponent's AC by 6 on the combat roll, she still does 4 points of damage.
This means that
- There's no longer any dissonance between attack and damage rolls. Who hasn't felt the thrill of a great attack roll and then chumped out with a 1 on the damage die? No more.
- Weapons with higher damage ratings reward higher combat skill. You can still use a Damage 8 weapon even if you're inept in battle, but it's less effective when you don't have a mathematical possibility of exceeding your target's AC by at least 8 points.
- You can have low-damage weapons that are easier to wield, or that are effective at punching through armor, receive a bonus to combat rolls, and high-damage weapons that receive no bonuses but are more deadly in the hands of a combat expert.
- You avoid the double-dip of Strength bonuses (and the double whammy of penalties) on attack and damage rolls, while still making Strength very relevant to melee effectiveness.
Combat options in this system include:
- Defend: Combat Rating is applied to AC instead of combat rolls for that round. Combat rolls may still be attempted, but without the bonus. Good for when you're overwhelmed and waiting for the cavalry to come to the rescue, or you want to toy with weaker opponents. (Advanced option: Combat Rating may be split between offense and defense.)
- Sweep: Attack more than one opponent in a round. Maximum number which can be fought is equal to half the weapon's Damage - you can threaten more opponents at a time with a battle axe than with a dagger. All targets must be within reach, i.e. no movement is allowed to reach others. Make a separate combat roll against each opponent, but all rolls are at -2 per opponent over one, i.e. -2 for two opponents, -4 for three, -6 for four, and so on. Obviously a tactic best used against weak opponents, or by a very skilled combatant.
- Beleaguer: Opposite of sweep, several combatants concentrate their efforts against one opponent. Each receives +1 to its combat roll for every member of the attacking group above one. Makes being outnumbered very dangerous.
- Interpose: Hold your position and fend off attackers with a weapon with long reach, like a spear. If your combat roll exceeds the opponent's, it can't get to you, and thus can't damage you, even if its roll would normally succeed.
- Disengage: If your combat roll is higher than your opponent's, whether or not either one scores damage, you may disengage from melee and back away 5'.
- Retreat: Turn tail and run! An opponent that chooses to attack you in melee gets +2 to its combat roll and ignores your shield. If you survive and you're faster, or the opponent chooses not to follow, you're no longer in melee. Avoid the attack from behind if you disengage first.
- Force movement: Whichever combatant scores the highest combat roll, regardless of damage, may force the opponent to move 5' in a direction of the winner's choosing.
Some of these tactics could be adapted to house-rule a more traditional D&D-like combat system, but I think they're particularly elegant with the G&G model.
Critical success and failure (optional): When a combatant rolls a natural 20, it strikes a particularly vulnerable point on the opponent. Roll its damage die and add the result to the normal damage caused. Optionally, the critical damage die explodes - roll again each time the maximum possible result is rolled, and add the result to the previous damage. If desired, a player may choose an alternate critical success result before the combat roll is made, such as disarming, snatching an item, pulling the opponent's helmet over its eyes, etc. If the roll is a critical success, the desired effect occurs, but no extra damage is done.
A critical failure causes something unfortunate to happen to the combatant who rolled it. Exact results are up to the GM and player. The target of a critical failure may be allowed to narrate a result. Game mechanical effects are at the GM's discretion; losing the next round of actions is typical, but others are possible.
Just about any action in combat should be able to be modeled by one of these applications of the combat roll - either vs. opponent's AC, vs. opponent's roll, or special result on a critical success.
Most of the foundations of this system are not of my own devising. The concept of an attack bonus rather than an attack matrix or THAC0 is used in quite a few games. Likewise, the idea of attack roll directly determining damage is something I read about elsewhere, though I can't recall where. My contribution is mainly to bring these elements together, and tie those mechanics into the various combat options above.
That's it for the basics. Next up, the iniative-less combat sequence.