Some PDQ Thoughts on Combat

WhitecoverI’ve been playing around with a DnD like port for PDQ. In doing so I started thinking about something like ‘GM tips’ on setting up combats using PDQ. Here are some of my ideas on setting the defensive skills of the opposition and how much damage they should be able to take.

Mechanics

In order to damage an opponent in combat a character rolls 2d6 and adds their attack ability, which will be divisible by 2 so 0, 2, 4, etc. The defender rolls 2d6 and adds their defensive ability, also done by 2’s. If the attacker’s total exceeds the defender’s the defender takes one point of damage for every point that it is higher. So if the attacker rolls a 10 and the defender a 7, the defender takes 3 damage. The damage comes off of a character’s abilities. Once a character runs out of abilities to damage they are defeated.

One wrinkle is that there are several editions of the rules. In some if there is a tie then both characters take a point of damage and they roll again until one has a better roll than the other. This analysis will be slightly off for anyone using that rule. Some editions have attackers take damage for every point that they miss by. So if the attacker rolled a 7 and the defender a 10, the attacker wouldn’t just miss, they would take 3 damage. In PDQ sharp characters get 3 dice for combat and can use 0 – 3 of them for their attack and the rest for defense. Either of these rules significantly alter combat and this analysis just can’t apply to games using one of those rules.

Another important wrinkle is that in PDQ almost any ability can be used in an attack like fashion. Opponents can be brow beaten into submission with persuasiveness or intimidation etc. For the D&D port this is less common as many opponents are relatively immune to alternative attacks, persuasion isn’t going to work on a wolf pack, even in PDQ. However, these calculations are based on the idea that the characters have a main skill that they use for most of their combat rolls. If the players constantly switch which abilities they are using for their attacks these results will be less useful. In addition, an unexpected use of a rarely used ability might make a fight easier than the calculations indicate. I don’t see that as a problem, rather a reward for thinking outside the box.

Chance to hit

Table 1 shows the chance to hit an opponent at a given difference between attack and defense abilities.

Table 1 Chance to Hit and Average Damage

Attacker’s Skill vs Defender Chance to Hit (%) Average Damage
-6 3 0.04
-4 10 0.2
-2 24 0.6
0 44 1.4
+2 66 2.6
+4 84 4.2

This has some implications for how high an opponent’s defensive abilities should be. I’ve learned through painful personal experience that players really, really hate missing. Given a choice between defeating an opponent by hitting them five times or missing four times and taking out a foe with the fifth attack, players will much prefer hitting five times, even though the final results are identical. They defeat the opponent in five attacks. This means that the GM should avoid using an opponent with a defensive ability 6 higher than the player’s best attack ability. Unless the goal is to force them to use an unusual ability to combat the opponent it will do nothing but frustrate them. Actually, it will probably frustrate them regardless. Even 4 higher is likely to be bad unless they have hero points or other ways of increasing their chance of hitting. So in general a ‘hard to hit’ opponent should have a defense 2 higher than the character’s attack ability.

Rule of Thumb: Don’t have opponents with defense more than 2 above the player’s best attack, for most opponents it should be lower than the best attack.

Time to failure

For the most part, opponents in PDQ are made in a similar manner to PC’s. However, this generally doesn’t work if the GM wants to have one powerful opponent fight an entire group of PC’s, like a huge Purple Worm attacking a group of adventurers. Either their defensive skill is so high that it drives the players crazy or the opponent takes so much damage so quickly that it really isn’t much of a fight.

Table 1 also shows the average damage done per attack depending on skill differences. This can be used to give a rough estimate of how many attacks it will take to defeat an opponent. For example, an equal skill attacker will take around 11 attacks to inflict 15 damage (15/ 1.4 = 10.7). Now, there are several caveats to this calculation.

No hero points: The calculation doesn’t take into account resources like hero points, which can be used to increase rolls or damage. If used by the attacker it will decrease the number of attacks needed, if by the defender it will increase them.

Only works for larger numbers: Because it is based on the average for a pretty variable roll the calculation really only works if the result is a reasonable number of attacks. For an opponent that is going to be defeated by only 1 or 2 hits the base chance to hit is a better measure of how long a fight will take.

Doesn’t include the death spiral: Damage in PDQ is applied to abilities. Once a target takes damage on the ability it is using to defend itself the chance of hitting and average damage increase considerably. If their defensive abilities are used as part of the total damage that a target can take the calculations will over estimate the number of needed attacks.

Assumes that attacker is basically unharmed: This is how long it is expected to take if the attacker wins and doesn’t have their attack skill damaged in the fight.

Because of the variability of the dice rolls, it is just a rough guess: Figure 1 shows the distribution of how many attacks it takes to inflict 15 or more damage on an equal skilled target. The most likely numbers are 10 or 11 attacks, just as predicted. However, it can easily take more or fewer. The range 8 to 14 just covers over half of the results.

Keeping the caveats in mind, this table can be used to get an idea of how tough an opponent should be. A group of four players with attack skills of +4, +4, +4, and +6, respectively, would be expected to inflict a total of 3.2 damage a round (3 x 0.6 +1.4 = 3.2) against a +6 defense target. So what if a GM wanted to have a Purple Worm with +6 Combat ability attack them and last around 5 combat rounds? Assume that damage to the worm’s combat ability would result in a quick death spiral so figure that the 5th round takes care of the combat ability. So the worm would need to be able to take 4 rounds of their average damage or basically 13 damage (4 x 3.2 = 12.8) to non-combat abilities.

If opponents need to be generated quickly, the average damage a group inflicts on differently skilled opponents could be calculated ahead of time. For example, the group mentioned above does 3.2 damage/ round versus a +6 defense opponent. Against an opponent with +4 defense they would do 6.8 (3 x 1.4 +2.6 = 6.8). So a table would look like Table 2.

Table 2. Example Group’s Average Damage Per Round

Defender’s Skill Average Damage/ Round
2 12.0
4 6.8
6 3.2
8 1.2

Rule of thumb: It’s a very rough guide, but Table 1 gives at least some idea of how long an opponent will last. Average damage per round can even be pre-calculated for the whole team when facing different skills.

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2 Responses

  1. Very nice indeed. As you know, I’m going to be running a PDQ fantasy game in a month or so, and after character creation, I may ask for a little help with a table like this customized for my campaign’s party.

    Is it at all possible to model anything as chaotic as a group in combat with another group?

  2. Thanks Mark.
    I’m sure that someone with serious programing skill and lots of time could model group combat. The big online games probably do the equivalent. I was mostly interested in single, large opponents due to the general difficulty the system can have with this genre staple.

    One easy way to balance a fight of team on team is to just clone the PC’s and then reduce the copy’s abilities a little and use them as the opponents. Though no matter how you balance it there is always the question of the match ups. If the party sage decides to single-handedly take on the best enemy fighter things wont go so well.

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