[Hayashi]

Base AC is 10, before modifiers due to high DEX. For instance, a character with a DEX of 18 (which modifies AC by -4) would have an AC of 6 without armour, spells, etc.

THAC0 is a measure of the ability to hit an opponent. A fresh level 1 character gets a THAC0 of 20 (iirc), but this score improves as the character gains levels. A fighter's THACO improves the best, whilst other classes (e.g. mages) improve more slowly.

THAC0 is modified by the weapon one uses (magical weapons give bonuses to THACO for example), his/her proficiency in that type of weapon and wearing items or drinking potions that improive THAC0.

THAC0 (To Hit Armour Class 0 [zero]) works like this: When trying to see if you have hit an opponent, a 20-sided die is rolled (hence the number can be from 1 to 20). The roll is modified by the opponent's AC. If his/her/its AC is greater than 0, than the difference is added to your roll. Conversely, if the AC is less than zero, the difference is subtracted from the die roll.

If the number rolled (after modifications) is greater than or equal to your THAC0 than the hit is successful. If not, than you've missed.

An unmodified roll of 20 is always a hit. What's more it is counted as a critical hit which does double damage. An unmodifed roll of 1 always counts as a critical miss, and you usually lose your turn.

Examples:

Your THAC0 = 12
Opponent's AC = 2
In order to hit your opponent you must roll 10 or better (12-2= 10).

Your THAC0 = 12
Opponent's AC = -1
To hit you must roll 13 or better (12-(-1)= 12+1 =13)

Your THAC0 = 2
Opponent's AC = 8
To hit you must roll 2 or better (2-8= -6, but 1 is always a critical miss)

In both instances (THAC0 & AC) the lower the number the better. It is possible to have negative numbers for these scores (which is good).

[ 08-22-2002, 09:09 PM: Message edited by: Hayashi ]