“Skill Checks” and “Rolling for Effect”

7 02 2011

It is very tempting to come up with a list of things that could occur in a miniature game and then develop a mechanic for each of these.  Many-a-game is published with a booklet of charts and modifiers that are used in each particular circumstance.  These games can be fun but they have the critical short coming that everything that happens must pass through the hands of the man with the charts. 

To give an example of this in the extreme, we spent some quality time a few years back playing Yaquinto’s Ironclads in miniature.  Ironclads was a pretty detailed simulation of naval combat during the American Civil war.  The guys who put this game together REALLY put some thought into the effects of cannon fire on an armored naval vessels.  The game was always fast… as long as no one was shooting.


For every shot fired the following had to be done:

  • Determine if the gun arc covered the target ship.  Confederate and union ships each have a set of firing arcs based on whether the gun faced the side of the ship or to the bow or stern.  Also, arcs could change if the gun firing was at the end of a battery.
  • determine the range of the shot (long, medium, close).  This varied by gun.  By the way, there where hundreds of guns used during the war…. each with its own chart.
  • See if you hit, missed or if your gun blew up.  Speed (both firing and target) the quality of the firing ships crew, moral of the firing ships crew and the silhouette of the target ship all modified this check.
  • See where you hit (Deck, casemate, waterline).  This time the angle of the ship and the type of ship matter .  (This is a crazy chart I still have dreams about.)
  • Determine damage to the armor of the ship.  The armor of the target ship, the type of gun and range count here.
  • Determine if there is damage to the inside of the ship.  The type of gun, the type of shell, the range and the armor of the target ship are all important.  This step was a biggy.  Shots that went “indoors” broke stuff. 
  • Check for “Special” hits.  Once a shot went indoors it broke things, namely crew, hull and armor.  Sometimes you got lucky broke something else.  This could be a gun, the engine, steering apparatus, ventilation, the pump that was moving water out of the ship, the smoke stack or a particularly important officer.  This step was also a biggy and tended to bring the house down if something cool got busted. 

note: smoke stack hits where my favorite.  Imagine the plume of smoke coming off the train from the Hogwarts Express being routed into a space the size of a one story home.  Cough… Ack… Wheeze…

  • Record damage on target ship and update modifiers.  Losses to crew and hull caused other types of damage to the ship.  Ships slowed down, their crews panicked and ultimately, they sunk.   Each of these effects had its own chart.

It was not uncommon for us to play a game with 20 boats each with 6 or 7 guns over 20 turns.  It was an all day sucker.

What problems need solving?

What are we going to be doing with our little game the most?  Once I come up with a list of things that have to be done then I can noodle around with a mechanic or two that will work along with most of these activities.

Here is a non-exhaustive list of things that troops and officers might do in battle…

  • Officers attempt to issue orders
  • Troops move as far as they can
  • Troops shoot and kill other troops
  • Troops try to withstand a demoralizing event
  • Officers rally routed troops
  • Troops react to the actions of enemy troops
  • Officers take casualties

Ok… happily there is a trend.  Either a unit attempts to do something tricky (succeeding or failing) or the units sees HOW effectively it did something (it didn’t do it, it did it a little, it did it a lot.).

The first of these I will call a “Skill check”.  Can that officer issue an order?  Can those troops adjust their flank before being fired on?  Those guys are taking a ton of fire, I wander if they can keep from running away.  I need a skill mechanic that will give me a yes/no result.

The second of these I will call “Rolling for Effect”.  How many men did that unit hit with it’s fire?  Just HOW far did that unit manage to move?  I need a mechanic that measures degrees of success.

A base mechanic

While war-games are still struggling with simplification as a core value, roleplaying games long ago made a dramatic shift to making sure everyone who participated knew how to play.  Skill based mechanics are key to this success.  In skill based roleplaying games, characters have discrete skill levels for a number of things they may attempt to do over the course of a game.  A basketball player character might have a shooting skill for instance.  Shooting a point after might be as simple as rolling below that characters shooting skill with a dice OR rolling a number of dice equal to the shooting skill and seeing how many dice resulted in “successes”.

I want this.

In the case of my game, this sort of simplicity will work EXTREMELY well.  None of my guys use magic or hack computers.

SO… In general… A skill role will be made using a number of 6 sided dice based on the experience level of the troops.  Troops can be Green (2 dice), Veteran (3 dice) or Elite (4 dice). 

To succeed a skill check, one (and only one) dice needs to be a “4”.  Done.

Troops rolling for effect will count the number of “4”s rolled.  The effect being  rolled for will have an interpretation of each success. For instance, rolling for bonus movement might produce additional distance for each success.

Rolls by officers will use the command rating I mentioned in the Bag o’ destiny blog instead of experience level.

There… I ‘m done.  Let’s play.


Things are done with a varying degree of “difficulty”.  There will need to be a way to modify a skill check to indicate something is tougher or easier.  Going back to my basketball player, that free throw is easy but not as easy as a shot from under the rim, and not as hard as a shot from the three point line.  I need a list of modifiers…  Let’s start with this…

  • “In the paint” +0
  • “at the free throw line” +1
  • Three point range +2

Lets say that my guy has a shooting skill of 3 (three six sided dice) and he needs a single success for getting the shot in the hoop.

With a modifier of +0, I can see that I need a “4” one of my three dice to sink a shot from under the basket.  This is means our guy has an 87.5% chance of hitting a layup.  Sounds reasonable.

Similarly he needs a “5” to hit a free throw which he will do 72.125% of the time.  Better than both me and Shaq.

From the three point line he will need a “6” and he will succeed 42.129% of the time.  Good!

OK… so far so good.  Let’s add a new skill…. PASSING.

Our boy has a passing skill of 2 which means he has two dice.  We already know he needs a single “4” to succeed.  There… I just taught you a new mechanic.

Let’s create some modifiers!

  • Passing from three point range to three point range +0
  • Passing from three point range to the free throw line +1
  • Passing from three point range to “the paint” +2

This seems really familiar… These modifiers are similar to the shooting modifiers.  Now… they didn’t have to be but because they are they are really easy to remember.  Hopefully as I come of with modifiers for all the various skill checks scattered through out my game I will bear this in mind.

Long odds

I left some shooting modifiers out…  silly me…

  • being covered +1
  • being double teamed +2
  • Having a broken leg +3

Let’s say our shooter has a choice between taking a shot at the free-throw line unmolested or going into the paint but drawing a defender… which should he do”?  Answer… doesn’t matter (unless he is worried about his highlight reel).  It’s a +1 either way.  He needs a “5” to hit the shot which he will do 72.125% of the time

Let’s say he is double teamed at three point range… how tough will this be?  The answer… tough.  He needs “4” +2 for the range and +2 more for the double team.  He needs an “8”.

Do we tell the guy… “tough… you need an “8” and your dice just don’t work that way”?  He will likely respond that not only is this shot possible, he saw a kid do it just the other day.  I need a mechanic to deal with the improbable.

What we need is a way to extend the curve of probabilities beyond what a single roll of a six sided dice will give me.  A die will roll a “4” or better 50% of the time, a “5” or better 33.33% of the time and and a “6” 16.63 % of the time.  This curve is moving towards “0” too fast for me.  I need to add a “7” somewhere between 16.6% and 0%.  Why not slice it in half?

A six sided die on my planet rolls a “7” or more 8.4% of the time.  All I have to do is flip a coin whenever I roll a “6” to produce this result.  50% if the time I roll a “6”, I rolled a “7”.  Sweet. 

This does our basketball player no good though… he needed an “8”.  What if I cut that 8.4″% in half again.  4.2% of the time I rolled an “8”.  Roll a “6”, flip a coin, and flip a coin again.  Using this logic there is ALWAYS as chance to succeed when rolling a skill check no matter how many modifiers I pile onto the check.

So… Doug… where did you steal find this…

Shadowrun.  Shadowrun does something a lot like this.  It works like a charm.  I’m totally reusing this for McPherson and Revenge.  Shadowrun has a different method for long odds determination that looks like junk on a graph so my “coin toss” resolution is my own refinement.




3 responses

7 02 2011
Jerry Choate

Let’s play. But, I get to be Michael Jordan.

1 02 2012
DavidDavid Sullivan

I’m inspired, Doug. I’m starting to write my own home-brewed rules and you’re giving me some good ideas that I’ll shamelessly steal from you.

1 02 2012
Douglas G. King

Good Luck. Let me know when you get started and we can cross link!

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