Jimmy Chattin

Roleplaying games are all about putting imaginations into fictional contexts of peril and adventure.

Sometimes, the characters imagined find themselves in a position of opportunity, or one of particular danger…

Thus, that character may have (dis-)advantage!

How that advantage gets reflected in the random outcomes of the situation is where the G – game – of RPG comes in. And that is where I’ve been struggling myself in consideration.

Follow me as I explore what kinds of advantage a game can have, and which my RPG system BITS might use.

Defining Terms

In RPGs, a character rolls dice and adds/subtracts value from those dice to randomly determine outcomes that are dangerous or might fail. In BITS, that roll is with 2d6 – two six-sided dice.

A roll can be altered in a few ways, one of which is having advantage, disadvantage, or neither. When disadvantage applies, it is virtually always the same-but-opposite of advantage (e.g. advantage gives a +2 to the final roll value? Disadvantage gives -2).

For brevity, when I talk about rolls, I will only talk about advantage – assume the opposite applies to disadvantage.

Advantage can come under many terms: Easy v. Hard Roll, Extra v. Less, etc. They all mean the same thing as advantage.

BITS has a few principles that apply to any game design with the system in mind:

• • Fewer Rolls (minimize the clatter of dice)
  • Less Math (adding one or two values is OK, subtracting values is iffy, multiplication should be avoided, and division must be avoided)
  • Rule of Two (BITS games are played with two and only two dice six-sided dice; link unrelated 🙂 )
  • Simplify (less is more for everything in BITS, the same systems reused for every context)

We must keep that list in mind when evaluating the following.

Mechanics For Advantage

In no particular order:

Reroll

The classic. Whatever you are rolling, roll all the dice a second time. Take the better result.

Dungeons & Dragons uses this and so do myriad other games. It is simple and can apply to any roll. Also, if the game uses ‘criticals’ (extreme success or failure on low-probability rolls; i.e. ~5% or less), rerolling increases the chance for these.

The only problem is that it involves picking up the dice and throwing again. While it can boost the feeling of anticipation a player has by waiting for that second roll, it can boost the feeling of disappointment too when the second roll fails to improve the situation of the first.

Increase Range

When rolling in an RPG, rolls are expected to hit target value ranges or they fail.

In D&D, X+ is needed where ‘X’ or more succeeds. Call of Cthulhu requires X-, where the roll must be at or lower than ‘X’. Tiny Dungeon succeeds when a roll of 5 or 6 happens; a special move can expand that range to also include 4 in a next turn.

For BITS, an ‘X’ target is an odd number and increases or decreases by 2 for each target level (e.g. 7 is easy, 9 is moderate, 11 hard, etc.).

To give advantage by increasing the range means hard things become moderate, etc.

This is cool because it is decently simple math and it may increase the chances of a critical success depending on system. (In BITS, doubles like 5-5 that are above the target ‘X’ count as criticals; the lower the ‘X’, the higher the chance of criticals!)

The downside is that does do subtraction for disadvantage (-2 in the BITS case; would be -5 in D&D‘s case). Can we find something better?

Add Flat Modifier

Pure math based on the average change introduced by a rerolling of dice.

For a d20 (the die D&D uses), rerolling the value of a d20 leads to an average 3.325 difference. That’s a +/- 3 or 4, depending on how the system wants to swing it. An example would be Index Card RPG with its flat +/- 3 modifier.

Rerolling 2d6 leads to ~1.37, so +/- 1 or 2. As an aside, if we look back at the Increase Range section, the +/- 2 matches up quite well 🙂

BUT, a flat modifier does not increase the changes of critical hits. Therefore, for the same math as the previous, gameplay does not increase in intensity with that added critical chance.

Multiply / Divide Results

Let me start by saying, “yuck!”

For the sake of completeness, I’ll touch briefly here.

Some games would have advantage multiply results together instead of add them if rolling multiple dice, or multiply/divide the final value by, say 2.

This has been primarily suggested for some d100 games (e.g. Call of Cthulhu where you have to roll under a number, so advantage would divide your result by half, helping you come under the target).

Is this not obviously sucky? Math must be kept to a minimum in a game lest it become a simulation. Not just that, but math must be kept to the simplest forms possible: addition, subtraction sometimes, and perhaps a multiplication by 10 occasionally (adding a 0 to the end of a value is OK).

Doing any other multiplication/division on results is preposterous. No apologies.

Analysis

Rerolling for advantage is the classic. Pick the better roll, add any modifiers to that. For saving the mental effort of extra math, time taken rolling is increased.

Increasing ranges and adding a flat modifier are closely aligned, though the former is a better option for players because of the manipulation of critical probabilities. Despite saving time in rolling though, it adds mental complexity with a bit of math being applied before the roll.

Let us let die the thought of using multiplication and division in any game ever.

So which is superior? …

That is a tough one. The rerolls get people to pay attention and can lead to dread or hopefulness for the second roll. The changing difficulty gives an immediate result, but removes anticipation and only increases chances at a critical for systems that don’t have a flat critical success number (e.g. D&D wouldn’t benefit because crits only happen on a value roll of 20).

With that in mind, perhaps the classic and tried-and-true method of rerolling dice has been roleplaying games’ default for decades for a reason. However, if a system would benefit from it, flat increases or decreases to difficulty target numbers is definitely worth one’s consideration.

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I’m still kind of torn for which advantage system to use for BITS. What do you think BITS should ‘roll’ with? What systems do you use in your games?

Looking forward to your advice. Happy gaming! Cheers 🎲🎲

With the conversion of d20 table-top roleplaying game systems into BITS’s 2d6, I figured we should follow up with another incredibly popular system of d100.

About d100

In d100, two 10-sided dice are rolled, one being the 10s spot on a number, the other being the 1s spot.

A player’s character has stats or attributes that represent how good they are at certain things. These could be numbers from 1 to 99, 0 and 100 reserved for critical failure or success on rolls.

There are two kinds of d100 system: roll target or under, and, roll target or over. Because the latter requires a lot more math for reasons I’ll leave out here, the rest of this post only deals with rolling at a target number or under 🙂

When a roll needs to happen, the rolling player picks their best applicable attribute. When rolling, the value of the roll must be at or under that target. So while the attributes of the character increase as they experience the game, so too do rolls get easier!

That’s d100 at a glance.

Roll %s

To get from d100 to 2d6, we need to talk percentages.

A d100 has an average value of 50.5, or that ~51 and above will happen half the time. Makes sense. 2d6 averages at 7, where any number at or above that comes out 58.33% of the time.

But 58.33% is a significant departure from 50.5%! However, if we consider percentages are rounded down, that 58.33% can become 50%. With that bit of fudging, percentages are back in safe waters.

Ability Score to BITS

This is where the conversion happens.

How can a player know what their d100 stat is in BITS 2d6?

Easy: consider everything below average is a 0 in BITS while dividing everything above into decreasing proportions.

A simple use of the 1-2-3-4 nature of BITS is we invert how much weight is put on each element. A 1 should have 40% ownership of anything next above average, 2 30% after that, 3 20%, and 4 10%.

Starting at the lowest percentage of 10%, 10% of the 2d6 average percent of 58.33 is 5.833. Since it has already been decided rounding down is key here, the value of 4 in BITS will own the last 5% of all scores and 1 will get 20% of the total.

That’s a bit wordy. Here’s a chart:

Easy, right?

And, depending on what’s available for a given game, group skills and abilities equally under each BIT (Body, Interaction, Thought) to get that BIT’s value. Average together the values there, round down (if needed), compare with the chart above.

Easy!

Other Considerations

Now I know some d100 systems use additional scores that aren’t based on 100. Some systems use poly-dice.

For those numbers in those systems, I refer you back to my d20 poly-dice conversion post. That can convert Dungeons & Dragons and it can convert here too.

Applicable Games

Any game that uses a d100 system!

(Though I must admit my exposure to d100 systems is much lacking compared to d20s and polyhedrals.)

If it is a weird one with a roll-over mechanic, there shouldn’t be too much fiddling with the values to get things back on track. Set everything below-average to 0, then divide-up the remainder with 40%-30%-20%-10%.

Some games using the d100 system:

• • Call of Cthulhu – Biggest RPG in Japan and a maddeningly good time.
  • Zweihander – Perilous dark fantasy.
  • Warhammer Fantasy – Grimdark murder in a fantastical world.
  • Wrath and Glory – Grimdark far future where there is only war.

Missteps Along the Way

That’s the end of the d100 conversion so you may move on to another article on this site.

If you’d like to know what was was reviewed before the above was settled on, keep reading ~

Don’t think that I had all of the formulas and math pop into my head at once. I looked up dice probabilities and ran multiple graphs to confirm what was both mathematically sound and friendly (i.e. easy) for player use.

However, starting off with the wrong premise can make any outcome moot.

The first failure was looking at the value of 1 as a percentage of 2d6. That’s 14.3% (1/7, the average value). Because it handles better, say 15%. 15% per point of BITS value (best calculated starting at 4 and going down to 1 at 60%.

This looked fine to start:

• • BIT Value – d100 Conversion
  • 0 – top 100%, nothing special.
  • 1 – top 60%, a 40 and above in d100 gets 1, OK.
  • 2 – top 45%, 55+, good.
  • 3 – top 30%, 70+, great.
  • 4 – top 15%, 85+, excellent.

But you can see already that a value of 1 allows below-average performance to attain above-average results. Further, the progression is linear, whereas 2d6 is inherently parabolic (lines and curves don’t mix).

Scrap that.

Next I figured out the value of 1 in 2d6 for above-average values. I.e., what is 14.3% of 41.67% (difference of 58.33% average)?

The answer is 6, but already the premise is wrong – I was using the below-average range to affect the above-average allocation of BITS values.

Lame!

But that didn’t stop me from using 42% with the 40%-30%-20%-10% conversion. This actually got really close to the final result, but I rounded down first (i.e. I stepped by 4% of the total):

• • 0 – >0
  • 1 – >60
  • 2 – >76
  • 3 – >88
  • 4 – >96

Ignoring that these numbers look kind of ugly, if we round up (4.2% is 10% of 42%, rounding up to 5%), we get what turns out to be the final conversion:

• • 0 – >0
  • 1 – >50
  • 2 – >70
  • 3 – >85
  • 4 – >95

So despite starting from the wrong place, we got to the correct answer 🤷‍♂️ Wild how that works!

Anyway, I caught these mistakes before and during writing, so now you can see some of the method that goes into the consideration of BITS and other systems 🙂

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The End

Appreciate you getting this far, reader.

For the d100 games you’ve played, what considerations are missing from the above? Did they get handled in last week’s d20 poly-dice blog? How could this all be improved?

Will be writing more on BITS for a while yet, so stick around! Cheers ~

My favorite game system BITS uses at its core 2d6 (two six-sided dice). With 2d6, monsters are slayed, gold plundered, and crowds wooed.

2d6 is virtually unseen in the most popular roleplaying games (i.e. the Don and uncontested king of roleplay, Dungeons & Dragons), only showing up in well received though still pretty niche engines like Powered By the Apocalypse.

Yet, where 2d6 does show up, the dice are used in mechanics that are nearly untranslatable to the bread-and-butter d20 and poly-dice systems in use by mainstream games a la D&D.

BITS fixes that by using similar modification and resolutions to D&D (the crunchier part) while using only 2d6 instead of an entire rock-quarry of *d* rolls.

Here’s how:

Roll %s

First, a comparison of percentages in rolls between D&D (which uses a d20 at its core) and BITS 2d6.

D&D uses various difficulty levels that a player has to roll at or above to succeed depending on context. The player can add different modifiers to their rolls to help them get the number they want. However, as a general guideline, challenges can be divided into the following:

• • Roll at or above.
  • 5 – Very easy, 80% success rate.
  • 10 – Easy, 55% success.
  • 15 – Moderate, 30%.
  • 20 – Hard, 5%.
  • 25 – Very hard, cannot be accomplished without some value boost.
  • 30 – Godly, cannot be accomplished without major value boosts.

The percentages above seem really low. That is, until you consider they take into account adding everything from -5 to +10 to the rolls based off the the six abilities a game character has.

Further, “natural” criticals are when a player rolls either a 1 or a 20 (ignoring all modifiers). These crits have a 5% each to give a player something especially harmful or helpful, relatively.

Now 2d6, both with and without D&D‘s heavy use of modifiers.

• • Roll at or above.
  • 5 – BITS has this as easy, 83.3% success chance. D&D would have this as very easy.
  • 7 – BITS moderate, 58.3%. D&D easy.
  • 9 – BITS hard, 27.8%. D&D moderate.
  • 11 – BITS very hard, 8.3%. D&D hard.
  • 13 – BITS very, very hard, and can’t be done without some help. D&D very hard.
  • 15 – D&D‘s god-tier difficulty needing top-level characters and lots of luck.

BITS also has criticals when “natural” doubles are rolled (1-1, 2-2, etc.) above or below the target difficulty number. This means criticals scale with the difficulty of the challenge encountered: easier targets offer more opportunities to really wallop ’em.

However, if the linear scale of D&D roll probability needs to be kept, natural 1-1 and 6-6 (both a 2.8% chance) can be adopted for BITS, no problem. But why? 2.8% does not equal 5%…

Take a look again at those percentages. 55% and 58.3%, 30% and 27.8%, even the 5% and 2.8% for criticals! The conversion from d20 to using 2d6 as a core mechanic is never more than 4%, a sneeze of a difference in gameplay. Fundamentally, swapping 2d6 for d20 has no noticeable effect on outcomes.

Therefore, as a core mechanic, 2d6 can substitute for D&D-like d20. Though, there are still modifiers to add 🙂

Abilities

D&D has six abilities that have both a base number and a modifier that slowly scales with the base. These six abilities are Strength, Constitution, Dexterity, Charisma, Intelligence, and Wisdom. Each ability’s modifier applies to challenges that are primarily in those abilities’ wheelhouse.

BITS has three abilities that are the modifiers added to the kinds of challenges that best fit their use. They are Body, Interaction, and Thought.

Now, the BIT of BITS has a 1:1 correlation with D&D: Body (Strength and Constitution), Interaction (Dexterity and Charisma), Thought (Intelligence and Wisdom).

If given a D&D character, the modifiers of that character’s abilities translate into a BIT value. By adding together the D&D modifiers, dividing by 2, and rounding down, new BIT values are found.

For example, let’s use the level 1 Fighter, Mage, Rogue, and Cleric starting characters for D&D.

Their stats (including health, aka HP, for later discussion):

BITS expects starting characters to have no more than 1 or 2 in any given BIT, so the numbers above for abilities work brilliantly. Not all classes in D&D are created equal, so in exchange for a BIT value perhaps a BITS specialty (the S in BITS; describes history or role and gives advantage when that context applies to a challenge) is gained, or unique equipment acquired, or HP gained (more on these things next).

Since some ability modifiers can be negative, thus resulting in a negative BITS value, what should be done?

Well, BITS could flatline the BIT value as “-“, meaning whenever a challenge would be solved by that particular BIT, the roll has disadvantage. Or maybe a “anti-specialty” where if certain situations come up, all failures are critical failures.

Even though BITS on principle refrains from using negative numbers, a conversion of d20 to 2d6 doesn’t need to use that tenet of BITS, maybe in this one case negative modifiers can remain 🙂

HP

Health, the lifeblood of player characters, the timer of how long a fight can possibly last.

The chart in the previous section has two numbers for BITS HP: the average of the die used in D&D (specified by class; d6, d8, d10, etc.) divided by 2, and that die average with the Body BITS value added.

That’s done because in D&D, HP is a certain die roll (d6, d8, d10, etc.) plus the Constitution modifier. For BITS, Body can be added to the average of the die for a class to achieve the same result.

Including the Body value in HP calculation can lead to HP bloat. While this may give more a feeling of heroic superiority to the player characters, it also leads to longer fights, less caution, and more flippant actions when the consequences aren’t that, well, consequential.

Depending if the Body value is added or not, and if there is any cap on HP (BITS typically likes to aim to cap at 12 HP), that changes the way combat and the use of equipment as a mechanic occur in the 2d6 conversion.

Equipment

BITS divides both fictional beings and their equipment into six tiers:

• • BITS Fantasy Weapon Tiers
  • 0 – Fists, unarmed combat.
  • 1 – Knives, small swords, cudgels, sticks, brass knuckles, hatchets, throwing spears.
  • 2 – Swords, axes, clubs, maces, short bows, light crossbows.
  • 3 – 2-handed mauls and bastard swords, pikes, longbows, flails, heavy crossbows.
  • 4 – Ballistae, claymores, halberds, tree-trunks.
  • 6 – Especially heroic or magical devices, such as Excalibur or Hercules’ club.
  • BITS Armor Tiers
  • 0 – No armor, clothing, robes, a buckler used as a shield in hand.
  • 1 – Leathers, round shields.
  • 2 – Mails, full-body shields.
  • 3 – Partial plates (a mix of mail and plate), 2-handed massive shields.
  • 4 – Full plate, a rolling barricade of treated wood used as a shield.
  • 6 – Heroic suits that are probably enchanted.

Gear can play into the BITS 2d6 conversion two ways. Either A) gear does nothing to a roll and gives its value as damage or reduced by 1 to negate damage, or B) gear adds to the roll value and the difference between the roll value and the target value is the damage given to a target (in the case of armor, it increases the chances of deflecting damage).

Let’s call option A the realism option, and B the heroic option.

Realism ought apply when a character’s HP is limited, either capped or very slow growing. Some characters ought die in a hit or two from a sharp object (just like real life!).

Heroic damage comes into play when characters feel overpowered. They smite small threats and can weather harsher punishment because their HP grows to accommodate.

Non-Player Characters

Whichever equipment mechanic is used to match the HP mechanic, non-player characters (NPCs; beasts, town guards, etc.) have their own tiers 0 to 6.

I personally am a =huge= fan of reducing enemy complexity in simulators games like D&D. Thereby in BITS, NPCs have HP equal to their tier and do damage equal to their tier. Players have to roll at or above the tier equivalent if wanting to either act against or defend against an NPC (e.g. a tier 1 may require a 7+ roll).

No rolling extra damage, no having to calculate HP, no having to figure out what every goon is wearing and carrying!

Keeping it simple like this should remain balanced between d20 and 2d6 implementations. Since I can’t vouch completely for it, if taking a D&D NPC into 2d6 territory, determine its abilities, HP, and equipment the same way done for characters detailed above.

(It does help that there are a plethora of NPC creation and balancing tools for D&D available, each ripe for conversion to BITS!)

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And that’s it! Just about all that’s needed to convert a poly-dice d20 system into a 2d6 BITS-like.

The joy of having the tools to do this means a lot of games can be converted into a concise system shared between multiple fictions and titles for faster-yet-still-hefty play.

What’s your take? Any sections of d20 and poly-dice mechanics from games like D&D missing here?

Hit me up and let me know! If you’ve any other suggestions or would like to see a test IP get converted into 2d6 and BITS (even if the IP doesn’t have a widely-recognized game with it!), I’d be happy to walk through the challenge of the conversion.

In any case, do well! Cheers ~