The BFRPG rulebook has optional rules for general task resolution in the Ability Rolls section on page 153. I use this but want to adjust the listed target number based on the difficulty of the task. As I want the bonuses and penalties to be somewhat consistent, I’ve put together a list of difficulty ratings based on D&D 5e’s Difficulty Class rule.
Each difficulty rating has a suggested Difficulty Adjustment (DA) value to add or subtract to the BFRPG Ability Roll target number. The DA doesn’t have to be exactly the numbers below. It could be any number in between.
- Very Easy (DA -10)
- Easy (DA -4)
- Medium (DA +0)
- Hard (DA +4)
- Very Hard (DA +10)
- Nearly Impossible (DA +14)
For example, Pedro the Level 3 Fighter with a Strength of 17 wanted to lift a heavy boulder that is blocking the group’s path. I decided that this is a Hard task. As a Level 3 Fighter, his ability roll target number is 16. As he has a Strength of 17, he gets a +2 bonus to his roll as normal.
Since this is a Hard task (DA +4), his actual target number is 20 (16 + 4). All he has to do is roll the die and add his +2 Strength bonus to it. If that adjusted roll value is 20 or above, he successfully moves the heavy boulder out of the way. So due to the +2 Strength bonus, he effectively needs to roll 18 (18 + 2 = 20) and above to move the heavy boulder.
There is really not much of a need to hide the actual target number adjusted by DA. However, for perception checks and some passive checks, the actual target number may be kept from the player making the roll so that the player doesn’t know if they actually succeeded or not.
Medium should be the default difficulty. Easy and Very Easy difficulties should not even need a roll to succeed unless the character is under stress and failure would be dramatic. Hard and Very Hard should only be used sparingly or in areas known to be very perilous (as the PCs go up in level). Nearly Impossible should only be used if the task shouldn’t be doable by anybody except the extremely lucky.
Thief abilities, racial abilities, open doors, and so on will continue to use the current rules as written except Ability modifiers could adjust the chances (Dexterity for movement-based rolls, Wisdom for detection-based rolls, Intelligence for knowledge-based rolls and Strength for force-based rolls). For percentage chances, each +1 modifier bonus is +5% improvement. For 1 of 6 chances, add the modifier to the chances so that a +2 of Strength gives the PC a successful open doors roll if she gets 3 and below (1 on a 1d6 becomes 3 [1+2] on a 1d6).