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Designing Out Loud – Skill System – Basic Mechanics

Okay, I seem to be running a bit late this week as well due to fallout from the camping trip (I developed a kidney stone the night we got back.  I don’t recommend this to anyone).  But better late than never.

My involvement with the experiment to create the SPACER RPG as a community via polls that I posted about two weeks ago has gotten me back to thinking about my game design and what I want to do.  So we’re back to our Designing Out Loud series this week to talk about the basic mechanics of the skill system.

I’ve gone back and forth on this several times trying to decide exactly how I want to do the skills but in the end I think that for now, I’ve decided to go with the broader skill definitions based somewhat directly on the character’s ability scores.  So let’s dive in and see what we have.

Skill Resolution Mechanic

Every skill will have the same basic mechanic.  You roll d100 and try to roll under the target number for the skill.  That target number will be determined by:

TN = 1/2 × relevant Ability Score + 10% × skill level + modifiers

The relevant ability score will depend on the skill being used.  For example, most weapons skills, especially weapons skills, will depend on your Dexterity ability although some melee weapons might call for using your Strength score.  A computer skill check might be based on your Intelligence while a scouting skill my rely on your Wisdom score.  And since the skills are fairly broad covering a range of actions, maybe the same skill in a slightly different situation will base off a different ability score.  It will be up to the referee and the player to decide which ability score is directly applicable.

Each level of skill will grant the character an increase of 10% in their skill chance.  Thus at lower levels the majority of success will come from their raw natural talent but at higher levels their skills and training will contribute more and more to their chance of success.

Finally modifiers can be applied to make the chance of success harder or easier based on situational modifiers.  Some of these may be defined in the skills (e.g. a negative modifier based on weapon ranges or computer levels) and some may simply be situational and assigned by the referee (e.g. blowing sand is making tracking your quarry across the desert slightly more difficult).


I’m still up in the air about this one.  On one hand I like the specificity of sub-skills.  It calls out specific actions and you can apply predetermined modifiers based on the action being attempted.

On the other hand, that may be to restricting.  It’s much easier if you just have a computer skill as opposed to a computer skill that allows you to do x, y, and z things.  What if you want to do w?  What skill (or sub-skill) covers that and what is the chance of success?  I can’t think of everything and there are sure to be things that players will want to do that I didn’t think of a skill/sub-skill for.

So for now, no sub-skills.  Instead of a computer skill with sub-skills like ‘defeat security’, ‘repair computer’, etc, we’ll just have a computer skill and when a player wants to do something related to computers, the referee will give an appropriate modifier to the basic resolution mechanic described above.

Skill Categories

Every skill will belong to a broader category.  For example the military skill area will include all the weapon skills, the technical skill area will cover things like computers, robotics, spaceship engineer, technician, and other related skills.  There will be a variety of skill categories.  The exact number and content is the subject of a later post but I’m looking at something like 8-10 categories.

At character creation each character will select one category to be their Primary Skill Category (PSC).  This represents the area where they have a high natural talent or disposition toward and want to focus their training.  In addition they will select two Secondary Skill Categories (SSC).  These also represent areas that they have an interest or ability in but to a lesser extent than their PSC.  All the other skill categories will be considered Tertiary Skill Categories (TSC) for that character.  A character can acquire and improve any skill be skills in the character’s PSC will be the easiest to increase, skills in their SSCs will be a bit harder, and skills that fall into their TSCs will be the hardest to improve.

These categories are used to define what is important and relevant to the character concept and what the player desires the character to excel as.  Maybe you envision your character as a hacker who likes to paint and is a gun enthusiast.  You pick the Tech PSC, with Military and Artisan as your SSCs.  On the other hand, maybe you want to be a roboticist that works with cybernetics and tries to keep abreast of all the relevant laws.  In that case you might have Tech as your PSC but have Bio-science and Scholar as your SSCs.

Improving Skills

Skills will be improved by spending experience points (XP).  The number of XP required to improve a skill will depend on the level of skill desired and which of the skill categories (PSC, SSC, or TSC) the skill falls into the for the character.  Basically there will be some multiplier times the desired skill level with the multiplier depending on the skill category.

As a working value, I’m looking at making the multipliers 3, 4 and 6 for PSC, SSC, and TSC skills respectively.  This means that if the skill in in your Primary Skill Category, getting level 1 will cost you 3 XP, level 2 will cost you and additional 6 XP, level 3 and additional 9 XP and so forth.  On the other hand, levels 1, 2, and 3 of a skill in one of your SSCs would cost 4, 8, and 12 XP respectively while a skill in one of your TSCs would cost 6, 12, and 18 XP for the same levels.

I haven’t decided on a maximum level yet but it will be probably be 6 unless I change the skill progression cost.  With the system described above,  Once you’ve hit level 3 in a TSC skill, you might be better off improving your ability scores (something I have talked about yet).  That assumes that you can trade 1 XP for 1 ability point.  For TSC, level 4 costs you 24 XP and gives you a +10% but you could get that same +10% by spending 20 XP on the relevant ability score.  For SSC skill, that point comes at level 5, and for PSC skills it comes at level 6.  This breaks down somewhat because different ability scores can apply in different situations but for the most part each skill will be based on a single ability score.

Now, if the cost of increasing ability scores is different than 1-to-1, this will change the balance a little as well.  That is something I’ll need to look at going forward.

Coming up

In the next Designing Out Loud article, I’ll be looking at the actual skills and skill categories.  If there is a skill you think is relevant to a sci-fi game, let me know and I’ll be sure to include it in the final list.

What do you think of this basic system?  Is it too simplistic, to complicated, not enough information?  Any other thought or things I should be considering when building the skills system?  Let me know in the comments below.



Categorised as: Game Design

One Comment

  1. [...] now that we’ve talked about the skill resolution mechanic and skill improvement costs, it’s time to start looking at the skills themselves.  As I mentioned in the previous post, [...]

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