You’ve seen me talk a lot about BITS, an original rule set for tabletop role-playing games (RPGs). It’s about time you got some more insight to it!
BITS, or Body-Interaction-Thought System, came about first when a colleague and knowledgeable friend mentioned how cumbersome the classic Dungeons and Dragons type of old-school RPG systems were.
I sat on this problem for awhile, pondering ways to automate and streamline the work of the world building, dice juggling, and stat monitoring. Nothing really “worked”β¦
Until I noticed that the universe of Warhammer 40K was made purely of the elements of Muscle, Machine, and Mind π€―
Looking at other RPG systems, I saw the 3Ms everywhere. All game systems divide into physical ability and performance, manual dexterity and know-how, and mental strength and intelligence.
For reasons I care to let you read or listen about, the 3Ms became the 4Ms, “Maybe” joining the ranks and becoming a dump section for anything narrative in a game.

I tried 4Ms for a few more things, but I couldn’t get Maybe to always feel “correct”, but I sure as heck wasn’t going to give up Muscle, Machine, and Mind!
What resulted was BITS. Body relates better to physical performance, Interaction better for manual work and social charisma, and Mind handling magic and intelligence. And in these things, any attributes or stats in any game can be put π
Further, I discovered a common theme of ‘4’ showing up in games, where every number could be normalized on a 0 to 4 scale. Thus, any single BITS value is rated 0 to 4 on a linear growth curve (0 to 1 is short, 3 to 4 is long), meaning any fictional creature in a game has at maximum a total of 12 for their values, while any single value is at most 4. (Great for balancing and restricting the dreaded Power Creep!)
BITS uses 2 6-sided dice (2d6) for every roll to see if a fictional creature succeeds at what it wants to do. The expectation is to keep things simple – 2d6 are easy to add together, they are the most common dice type, and having everyone roll only 2 dice for everything is elegantly simple (checkout the probability curve that games such as the famous Powered by the Apocalypse system uses).
When rolling, the “additions” to the roll are kept in a very exclusive list:
- Add a single BITS value (or none, in the case of pure Luck rolls), 0 to 4.
- Add 1 for any other creature that spends valuable time helping your creature act.
“Maybe” hasn’t gone away completely, either. The current test-case conversion of D&D into BITS has “Luck”, a fallback for whenever a roll needs to happen that doesn’t seem to fit into the Body-Interaction-Thought set, or is an event that a player would have no chance to react to. It means no values are added to the roll.
But what does a person need to roll to succeed?
“Threat” is the WIP term for the success threshold. Every creature and environmental obstacle has a threat which corresponds with their total BITS value (if a creature) or difficulty (hazards). Any action against this creature or hazard must roll (with additions) at or over the threat. (Easy, ya?)
Scaling threat has been a major undertaking with BITS and may not be done yet, so it goes for now as follows:
- Roll a 5 for easy actions.
- 7 for moderate.
- 9 for hard.
- etc.
Players max out at 13 threat. Simple!
The rolls may be altered (rerolling for dis-/advantage) or may lead to automatic successes/failures (doubles over/under threat).
Regardless, how effective the action is deals with how much over threat a roll is. Using damage from a weapon as an example, weapons only have a low base damage X from 1 to 4. However, for every degree of success over threat, that’s extra damage to add! No extra rolling for damage, no variable dice for damage, and a counterbalance of using tools and picking fights!
If you take damage, you must have health! Or, as it is in BITS, “wounds”, which you add any damage to (reduced by an armor value). Once you reach your maximum number of wounds, well, πππ
I aim to have wounds traceable with 6-sided dice for easy counting, so maximum wounds have been necessarily lowβ¦ I will need more playtesting later-/post-pandemic to understand the implications of that, but you get the drift – everything is to be easier, simpler, and more accessible π
When your creature acts is also streamlined. Everyone rolls, adding their highest BITS value. The highest final number goes first, but then if the result is even or odd, that changes the direction of the turn order (to the player’s left or right). If it’s the Game Moderator’s (GM) turn, they take a turn for every creature not controlled by a player.
The GM does more than moderate – they arbitrate, describe, listen, and help ensure the quality of the game. They’re also the player I aim to develop the most automation tools for π
Together, the GM and other players take on adventures meant to be self-contained missions that offer opportunities to pursue other adventures. The players gain XP for trying more difficult adventures, which increases their BITS values, which leads to getting more treasure in the adventure, which allows better equipment to be bought, which allows more difficult (and epic!) adventures to be undertaken, which gives more XP. #Cycles
And that’s a quick and dirty introduction to BITS! I have grand expectations for this theme-agnostic system, but am taking humble steps to make sure the foundations are solid before releasing the full set.
After reading all that, what are your thoughts? Any glaring holes in this design? How would you improve it?
Share your impressions and let me know if you’d like to be an alpha-reader. (Don’t worry – the system is split into short, topical guides.)
Take care of your own goals in September! Look forward to more design talk of BITS in the following weeks π Cheers ~
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