rules

Ascending Armor Class

by Jim on

I have resisted adopting ascending Armor Class due solely to my own observations of the evolution of Dungeons and Dragons. In short, "to hit" starts as a number line (Basic1) then becomes a set of tables hidden in the Dungeon Master's Guide (AD&D), then THAC0 (2E), bonus numbers on a class chart (3E) and finally class based advantages "to hit" disappear (4E and greater). From 4E onward fighters get quasi-magical powers that make them more difficult to play than in previous editions. I consider this bad game design because it increases the complexity of the once simple entry level class and thus raises the barrier to entry for new or casual gamers.

Additionally I think there's a real probability for social consequences such as fighter players convincing themselves that they get +level "to hit"2 or other players assuming their bonuses are incorrect.

Untested assumption are just that, untested.

Examining A.C.

For our thought experiment we'll assume a 6th level Fighter with no strength bonus. Using descending A.C. the fighter has a 15 THAC0. Using ascending A.C. the fighter has +5 to hit.

Descending A.C.

The range is -10 to 10 inclusive. The formula, THAC0 - Roll = AC. Examples:

  1. THAC0 (15) - Roll (15) = AC 0
  2. THAC0 (15) - Roll (12) = AC 3
  3. THAC0 (15) - Roll (19) = AC -4

Ascending A.C.

The theoretical range is 10 - 30 inclusive. The formula, Roll = AC. Examples:

  1. +5 + roll (10) = AC 15
  2. +5 + roll (7) = AC 12
  3. +5 + roll (14) AC 19

Examination

It seems obvious that ascending A.C. is the easier system, so let's examine how it was actually done by Wizards of the Coast. In 3E the 11th level Fighter has +11/+6/+1. That is +11 for their first attack, +6 for the second and +1 for the third. Worth noting, the Fighter's first attack is +level with following attacks being +level - 5. In 3E the 11th level Rogue (Thief) has +8/+3 and this does not obey the same math as the fighter.

I've not played 3E but I've heard from those who have that the worst of it was the math. Let's consider then that the player must remember which attack they're rolling, which bonus's they're adding and that they must roll their attacks one at a time to keep track of it all. If the Fighter has a +1 sword and +2 to hit (from Strength) each attack becomes; Roll 1 (13) + 11 + 1 + 2 = 27, Roll 2 (2) + 6 + 1 + 2 = 11 and Roll 3 (6) + 1 + 1 + 2 = 10. Consider next the thief with a +1 from strength and a +3 dagger; Roll 1 (19) + 8 + 1 + 3 = 31 and Roll 2 (3) + 3 + 1 + 3 = 10. Is this math easier? Will casual players remember it? Will social pressure, "Why is my roll different from theirs," undermine it?

The answers may be individual but the direction of 4E+ is a matter of record. Level based bonuses were removed in favor of class-based "powers" and video game like balance that in turn added their own level of complexity. Supposing we want to keep our games as "old-school" as possible (which I do) let us agree that the direction of Wizards of the Coast games is the incorrect path and examine ascending A.C. in a more AD&D context.

A translation of the AD&D Fighter's to hit table to ascending A.C. might look like like, +2 to hit at every odd level from levels 3 - 17; so +2 to hit at level 3, +4 at level 5 and so on until 17 where we may (or may not) cap the to hit bonus at +16. This ignores outliers such as needing a number greater than 20 to hit Armor Classes -5 or better at low levels, but fielding monsters at this A.C. against low-level player characters seems punitive, making this safe to disregard. The 11th level fighter's attack rolls (from above) would look like this Roll 1 (13) + 10 + 1 + 2 = 26 and Roll 2 (2) + 10 + 1 + 2 = 15. The math is of similar complexity to 3E save that is can be simplified by the player to a +13 to hit with the given +1 weapon making our rolls Roll 1 (13) + 13 = 26 and Roll 2 (2) + 13 = 15. If these were done with THAC0 (10 for the 11th level fighter) our math looks like THAC0 (10) - Roll 1 (13) + To Hit (+3) = -6 and THAC0 (10) - Roll 2 (2) + To Hit (+3) = 5

Is ascending A.C. really easier? I'd say yes but only fractionally since, as you can see, we're dealing with lower numbers using THAC0.

Cognitive Load

We've looked at math but the examination is incomplete if we don't also consider cognitive load with specific focus on that of the Dungeon Master. The player has only to focus on their character but the D.M. has to juggle the demands of all players, non-player characters, setting and so on. AD&D assumes the player will announce their roll, the D.M. will consult monster A.C. and a chart then tell the player if they've hit. Using THAC0 (2E) or a number line (Basic1) the chart look up is removed reducing the Dungeon Master's load to just consulting the stat block. The real win therefore is removing the chart lookup. D.M. referencing a goblin with 6 descending A.C. or 14 ascending A.C. has no notable difference.

So if we place the "to hit" load on the player then the ascending vs descending A.C. question is one of quality of life for the players. And though the above shows the actual difference in ascending or descending is mathematically nominal, actual experience will show that players feel better about ascending A.C. Addition feels simpler and higher rolls feel more triumphant.

I can only conclude therefore that I must surrender to ascending A.C. but not without the follow on concern that different level based to hit tables lead to the same problem path of 3E thus putting the game on the path to uniform systems and complex class design.

Ascending Armor Class will appear as an experimental rule in version 0.5.0 of my house rules.

Footnotes

  1. Basic herein represents Holmes Basic, B/X, and BECMI.
  2. You could change base 10 A.C. to base 11 A.C. but that introduces a cascade of other math.

by Jim