Mechanics-Preserving Combat Simplification

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cpt.crush cpt.crush's picture
Mechanics-Preserving Combat Simplification

[Edit: Updated numbers from first post since the Vanilla probability distribution was flawed, effective difference was small though.]

While I love Eclipse Phase, the high (GM) task load during combat has always bothered me a bit.

In particular making two dice rolls for the most common action during combat (attacking) made me wonder if THIS part of the mechanics could be simplified, while keeping the OVERALL mechanics mostly in place.

Design Goals

  • Minimal changes (i.e., no major rewrite).
  • Localized changes (i.e., affect only outcome determination, don't touch weapons / armor balance).
  • Easy to comprehend, logical and consistent (in line with other rules).
  • Reduce GM task loading.
  • Attack skill (e.g., Guns) and Defense skill (e.g., Fray) must still be useful.
  • Overall outcome must approximately be the same.

After doing some math, looking at tables and playing with values, here is what I suggest:

  • The Opposed Test during Attack becomes a Success Test.
  • Defender's Fray becomes, and is applied as, an Attacker's modifier.
  • Modifier is calculated as (Fray / -2 + 20)

For the overall math I have an Excel sheet to try and play with:!ApNUXXmnOvVxha8FTLOwFKx8SHMZVA

Here are the results visualized:


  • The general idea is, any roll of 2x D100 to determine a probabilistic outcome can instead be determined by a single D100. The 2x D100 can simulate a number of probability distributions, a single D100 is mostly linear. To have an approximately similar outcome, we need to match them somehow. This is what we try with the above rule / formula.
  • The Offset +20 seems to even the field the best way for "average" values. For an attacker with "average" Attack(50), and a defender with "average" Fray(50), the overall chance to hit is still around 45% (Vanilla: 40%). Other offsets are possible, shifting the field (download and play with the Excel sheet).
  • For extreme values of high/low Attack/Fray the there is a higher chance of auto-hits and misses than in Vanilla. However, both are (in my opinion) realistic, and can easily be compensated by established rules such as aiming, cover, or full defense.
  • Hitting another player / NPCs now does not mechanically differ anymore from hitting a moving skeet, while still taking into account the target's Fray skill.
  • To counter fact that bad defenders are now easier to hit than skeets, grant +20 for attacking "not actively evading" targets.
  • Factors that affect the defender, would instead apply "inversely" or "inversely halved" to attacker (e.g., defender behind moderate cover: Attack(-20)). Admittedly, that would require rebalancing these factors, but there are only a few of them. Factors that affect Fray on the defender's side (wounds, traumas, ...) would simply alter the computed modifier normally.
  • The system is more linear, rewarding higher (or penalizing lower) Fray.
  • It is slightly more deadly, leading to shorter fights.
  • It also incentivizes the use of environmental factors at low Fray, or against skilled Attackers.
  • Emphasizes more the fact that you can't really dodge bullet actively (i.e., make roll) once it left attacker's gun. Modifier still accounts for the fact you made attacker's life harder (or easier) by your training.
  • Fray modifier can be-precomputed and noted on character sheet.
  • Fray modifier can itself be modified by size-based modifier.
  • Allows GM eye-balling. For even more streamlined combat GM can now simply summarily announce overall modifier.
Additional Options
  • Make / keep full defense as opposed test (now even better reflect the *action* of going full defense).
  • Melee could either be converted, or kept as opposed combat.

What do you think?

Trappedinwikipedia Trappedinwikipedia's picture
Looks mathematically solid to

Looks mathematically solid to me. I'd want to try it out at the table though.

ThatWhichNeverWas ThatWhichNeverWas's picture
The Math doesn't tell the whole story...

I know a couple of people who wouldn't like this, because rolls against a set value gives the impression they have no influence over the roll's outcome.

In this case the argument has some substance, because as written the defender can't use pools or other mechanics to interact with the Roll.
There's also an issue with how modifiers are calculated; in an unopposed roll the Subject can theoretically negate any penalty by applying Bonuses. In an opposed roll, modifications applied to the Defender cannot be counteracted by the Aggressor.

In the past we've had to compensate for weaknesses, finding quick solutions that only benefit a few.
But what if we never need to feel weak or morally conflicted again?