Combat overhaul: attack algorithm

Dice tech basics

When you make a check of TN/D difficulty, you want to roll TN or lower on a D-sided die. Call that a hit, otherwise, the die is a miss.

Sometimes you'll modify the roll by adding bonus dice (roll an extra die of the same size and take the better result), penalty dice (roll an extra die of the same size and take the worse result), or changing the target number (TN).

If you would increase TN to the point where the task is a sure thing (in other words, TN = die size), bump up the die size instead and increase the TN accordingly. (So a task gets easier as 4/6, 5/6, 7/8, 9/10, 11/12, 19/20...) Similarly, if you would ever decrease TN to the point where the task is impossible (in other words, TN = 0 or less), keep TN the same and increase the die size. (So a task gets harder as 2/6, 1/6, 1/8, 1/10, 1/12, 1/20...)

If you have both bonus and penalty dice, cancel out one of each until you have only bonus dice, only penalty dice, or neither.

Now, roll the dice.

If you have any penalty dice and any misses, you fail. If you don't have any penalty dice, and you roll all misses, you fail. Otherwise, you succeed.

If you succeed, your degree of success is your number of hits. If you failed, your degree of failure is your number of misses.

If you roll all hits or all misses, roll 1/6 exploding to increase your degree of success/failure.

Combat considerations

On an individual attack, we care about:

  • Attacker skill (usually an "attack bonus" in dnd)
  • Attack type
  • Defender defenses, including armor, size, speed
  • Form superiority between fighting styles
  • Any miscellaneous advantages or disadvantages, like having the high ground

Figure out the details on all that.

The attack roll is a check. Start with a 3/6 difficulty, and modify it as follows:

  • If the attacker has form superiority, +1 TN. If the defender has form superiority, -1 TN.
  • If the defender is so small or so large that it is difficult to hit them at all, -1 TN.
  • If the defender cannot dodge effectively, +1 TN. If the defender can dodge unusually well, -1 TN.
  • If the attack penetrates the defender's armor with ease, +1 TN. If the defender's armor is particularly effective against the attack, -1 TN.
  • If the defender has magic armor, -1 TN per degree of magic (so a +5 shield gives -5 TN).
You get dice on the attack roll equal to your attack bonus, including any benefit from magic weapons and situational advantages. Don't worry about penalty dice from situational disadvantages; we'll just give bonus dice to the other side instead.

The roll, step 1

Everybody on a side makes their attack rolls. (Probably you've all got functionally identical weapons and armor on each side, so you can usually just roll it as one big pool of dice.) Add up the total number of successes. Distribute hits evenly between enemy targets, with the following considerations:

  • If you have n people attacking, you can only hit a maximum of n enemies
  • Spread hits between enemies as evenly as possible
  • First target combatants with light defenses and/or form inferiority over combatants with strong armor and/or form superiority

The roll, step 2

 Count up the number of hits the other side made side. The side dealing the most hits deals full damage: usually 1d6 for the first hit on a combatant, +1 for every additional hit. The side dealing fewer hits only deals 1 damage per hit.

In the event of a tie, 1 damage per hit on each combatant.

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