TW2K 4th edition’s rules are based on Free League’s Year Zero Engine and the RPG uses a step-dice mechanic when a player has to roll for a task, whether it is for using an attribute or a skill.
Okay, one step back.
CORE ATTRIBUTES
Every player has four basic attributes:
Strength (STR), Agility (AGL), Intelligence (INT) and Empathy (EMP)
If you stick to the encyclopedic definition of each attribute, they can be misleading. Gameplay-wise they each represent a broader spectrum of attributes that allows them to cover all possible rolls a player has to make. Indeed, each and every roll will always be for either just an attribute, or a skill-attribute combination, as each of the 12 skills is linked to an attribute (more on that later), and never for a skill alone.
Therefore, the STR attribute covers not only the physical strength of a player, but also his stamina and constitution. The AGL attribute incorporates coordination and reflexes, INT covers both the player’s pool of knowledge and his wisdom, and EMP broadly covers all so-called people skills.
Each attribute has a corresponding level, expressed by a letter ranging from A (highest level) to D (lowest level) assigned by a combination of player’s choice and dice roll in the character creation process.
A quick glance at a character’s core attributes can identify what kind of person this ink and paper alter-ego is.
For instance, this character:
STR: C
AGL: B
INT: A
EMP: D
Could be described as:
A sharp fellow, observant, witty and intuitive. Moves nimbly enough not to be seen by most, shows enough dexterity to be noteworthy. Rarely concerned with the well-being of others, and not really a people-person. Better not ask him to help you moving, or run a marathon, but he should handle a light jog.
Also, STR and AGL determine your hit points, while INT and EMP your stress points. Keep in mind that both will remain unmodified during the campaign.
SKILLS
Each player has a set of 12 skills, divided into four groups of 3, with each group correlated to a core attribute. As for the attributes, skills are rated with a letter A to D, but can also have no level: in this case the player has no training or experience in that particular skill.
The level of each skill is determined in the character creation process and can be later increase spending experience points accumulated in the campaign.
Each skill and attribute level has a corresponding die to roll:
Example #1: the player is in a firefight with his opponent: the player has to roll for Ranged Combat (skill) which is correlated to AGL (attribute). The player has Ranged Combat: C and AGL: B, and therefore rolls a D8 (Ranged Combat) and a D10 (AGL).
Example #2: the player is trying to give first aid to an NPC, so he rolls for First Aid (skill) which is correlated to EMP (attribute). The player has no skill level in First Aid, and EMP: C, so he rolls a D8 (EMP) alone.
SUCCESS(ES)
In order to succeed at the task, a player must roll at least one success, meaning at least one of the dice rolled must result in a 6 or higher. You can see how a higher level gives you better odds of a 6 or higher (a D6 has a 16,7% chance of resulting in a 6, while a D12 has a 58,3% chance of giving in a 6 or higher result). Also, having a skill level means you roll two dice instead of one when employing said skill, resulting in better odds (it doesn’t matter which dice results in a 6 or higher, both skill die and attribute die count the same).
If you roll 10 or higher, you get two successes. So, with a combination of D10s and D12s you can roll up to 4 successes. Multiple successes are important with opposite rolls, where a player and his opponent both roll for the same task, and he who gets the most successes wins the roll. Any extra success rolled while attacking with a weapon results in extra damage inflicted to the enemy.
Example: the player is trying to persuade an NPC to change his mind: they both roll for Persuasion (skill) which is correlated to EMP (attribute):
The player has Persuasion D and EMP: C, so he rolls a D6 (Persuasion) and a D8 (EMP).
The NPC has no skill level in Persuasion and EMP: D, so he rolls a D6 only.
In an opposite roll, you must roll more successes than your opponent to win the roll. Let’s say the player rolls 1 success, but the NPC is lucky and rolls 1 success as well; the NPC wins the roll and is not persuaded.
The dice set included in the Core Boxed Set of TW2K 4th Edition conveniently marks all dice’s faces showing 6 or higher with the success symbol 
, with faces showing 10, 11 and 12 marked by two success symbols.
MODIFIERS
Every roll can be affected by modifiers, both positive and negative, that are applied to represent the fact that the circumstances in which the player takes action are favorable/unfavorable and tip the odds towards success or failure respectively.
The examples I so far provided where all of unmodified rolls, or rolls where no modifiers where applied. A roll’s relevant modifiers are decided by the Referee, using the game’s manuals and his own judgement.
When you apply a modifier, you step the die you would normally roll up (+1) or down (-1) by the total sum of the relevant modifier. This means that if you would normally (absent any modifier) roll a D8, with a +1 modifier you would roll a D10 and with a -1 modifier a D6. If both modifiers apply their total is 0 and you still roll a D8.
When rolling two dice, you apply the modifiers with the aim of keeping the two dice as close as possible (you step up the lowest and step down the highest). You can roll no higher than two D12 and no lower than a single D6; any extra modifier doesn’t have any effect.
A couple of examples should clear any doubt:
Example #1: the player is firing at an enemy with his pistol. The player rolls for Ranged Combat (skill) and AGL (attribute); he has Range Combat C and AGL: B, so he should roll a D8 (skill) and a D10 (attribute).
Let’s apply a few modifiers:
a) the enemy is at medium range, resulting in a -1 penalty for the roll
b) the enemy is prone, resulting in a -1 penalty for the roll
c) the player has the Sidearms specialty, granting him a +1 for the roll
Total modifier is (-1) + (-1) + (+1) = -1
When stepping down one starts with the highest dice first, so the D8 + D10 (unmodified) roll becomes a D8 + D8 roll (modified).
Example #2: the player is trying to move unnoticed from one position to another, but there is an enemy sentinel in a watch tower that might spot him: this is an opposite Recon roll, and Recon (skill) is correlated to AGL (attribute).
The player has Recon C and AGL: C, so he should roll two D8.
The Sentinel has Recon C and AGL: D, so he should roll a D8 (skill) and a D6 (attribute).
They both have some modifiers that will influence their rolls. Let’s start with the player:
a) the player is moving through some shrubs that help his concealment, resulting in a +1 for the roll
b) the player is wearing camouflage, resulting in a +1 for the roll
Total modifier for the player is (+1) + (+1) = +2
Modifiers for the sentinel:
a) the sentinel has an elevated position (watch tower) granting him a +1 for the roll
Total modifier for the sentinel is +1
The player steps up both his dice by 1 (keeping the dice even) and rolls D10 + D10
The sentinel steps up his lowest dice by 1 and rolls D8 + D8
The player needs to roll more successes than the sentinel to remain unseen.
PUSHING ROLLS
If a player’s roll results in no successes (or not enough successes), the player can choose to push it. He gets to re-roll the dice and have another shot at succeeding. The catch? The re-rolled result is the final one whether better or worse than the previous, and any 1 rolled when pushing (marked with the 
symbol in the TW2K official dice set) results in a penalty for the player in the form of stress, or damage to himself or his equipment.
Here are the basic rules for pushing:
- Any die showing either a (or two) or a cannot be re-rolled when pushing.
- Any rolled after pushing results in the player suffering a point of damage for any physical task (e.g. marching, hand to hand combat, moving undetected) and a point of stress for any intellectual task (e.g. negotiating, medical aid, using command to rally another player).
- If the player is using a specific tool to perform the task, the tool suffers damage.
- A single roll can only be pushed once.
- In an opposite roll, you can decide to push your roll after your opponent’s roll.
Pushing the roll is a choice up to the player, and its use should be carefully considered. Here are a few examples:
Example #1: the player is engaged in hand-to-hand combat with a foe. On his turn, he decides to strike his opponent and rolls for Close Combat which depends on STR.
The player has Close Combat C and STR B, so he rolls a D8 and a D10 (let’s keep it simple and say no modifiers apply). He gets a 1 and a 3 respectively, so no successes. His swing misses the target.
Pushing the roll would allow him to re-roll the D10, but not the D8 (he got a X and it cannot be rolled). The X he rolled would be automatically carried in the final roll and result in a damage point suffered by the player. At the same time, re-rolling the D10 has a good chance of resulting in a success.
The player knows his foe is on his last leg, and even a single damage point would probably knock him down; also, a fellow second player is nearby and in trouble and our player wants to land a hand as soon as possible.
He therefore pushes the roll, re-rolling the D10 and getting a success (he rolls a 7).
Final result of the attack: the player strikes his opponent but suffers one damage point in the process.
Example #2: the player is moving across a patch of vegetation, trying to remain unseen by a marauder stationed nearby as the group prepares an assault on the bandits’ camp. He sees a good spot and on his turn proceeds to move there. The marauder might spot him, so this is an opposite Recon roll (Recon depends on AGL).
They both roll for Recon and AGL with the applicable modifiers. Let’s say the final modified rolls are as follows:
a) the player rolls D10+D10 and gets one success (rolled 2 and 8)
b) the marauder rolls D8+D8 and gets one success (rolled 7 and 4)
Despite having better odds, the player was unlucky, as a draw is in favor of the marauder, who sees him and will surely raise the alarm.
However, the player decides to push the roll: re-rolling a D10 still offers good odds, and now he needs a success on the re-roll to beat the single success rolled by the marauder.
The player re-rolls the D10 and gets 1. Still unlucky, his final roll is a single success, which is not enough to remain undetected, and the 1 he rolled on pushing means he suffers one point of damage.
Final result: the player is detected and injures himself (maybe he trips and falls, and the noise alerts the marauder).
Example #3: in the final phase of a firefight, the player is trying to persuade the two remaining active enemies to surrender. With a bit of roleplaying, he makes his argument and tries the convince them they are surrounded and have no escape. It’s a gamble, as in reality there’s just two players facing the enemies, but one is injured and ammo is running low. The referee rules that, as the player is bluffing, this is an opposite Persuasion roll against the enemy in charge.
After applying the relevant modifiers, the final rolls are as follows:
> the player rolls D10+D8 and gets no successes (rolled 4 and 2)
> the enemy leader rolls D8+D6 and gets no successes (rolled 5 and 5)
The player needed more successes than the enemy leader: a draw means he’s not convinced and knows the player is bluffing. The situation is dire, and the odds are good, so the player pushes the roll.
He re-rolls both dice and gets a success but also a (rolled 9 and 1). He wins the opposite Persuasion roll but suffers one point of stress in the process.
Final result: negotiations are tense, and the player’s nerves are put to the test. Eventually, the enemies surrender.
Twilight: 2000 can be an unforgiving RPG: if the right (or wrong) sequence of dice is rolled, it can result in the demise of the player without appeal. Pushing the roll is a mechanic reserved to the players (no NPC can use it, no matter if major or minor) and in my opinion serves to offset the (unlikely yet possible) brutality of an unlucky dice roll.
AMMO DICE
The TW2K official dice set contains six ammo dice: D6s showing the 
symbol on the face with the number 1, and a bullet symbol instead of the 6. These can be used in attacks with a ranged weapon and offer an increased chance of both scoring hits and inflicting damage. The trade-off is a higher ammo consumption, as adding the results of the rolled ammo dice represents the bullets fired in the round.
Every weapon in the game has, among its various statistics, a Rate of Fire (ROF). When attacking with a firearm a player rolls the base dice for the attack (e.g. Ranged Combat and AGL) and can add to the roll a number of ammo dice up to the ROF of his weapon, or the ammo count left in the magazine, whichever is the lowest.
The success of the attack is determined solely by the result of the base dice.
If the attack hits the target, then any 6 rolled on the ammo dice can be used for either inflicting extra damage to the enemy, a second hit on the same enemy, or hitting a second target in the same hex of the target enemy.
If the attack misses the target, any 6 rolled on the ammo dice can be used for suppressing the enemy. The attack doesn’t inflict any damage, but the enemy is suppressed, goes prone and loses both actions for his next round.
Note that enemies that are hit in a ranged attack are also suppressed (even if no ammo die is rolled). Suppression is usually automatic for NPCs, though the Referee has the final word; for instance, a major NPC might be allowed a CUF roll to avoid suppression.
Each player (and NPCs if the Referee is inclined) has a Coolness Under Fire (CUF) level, that comes into play when risking suppression. CUF is measured with a letter A to D and the player rolls the corresponding die: if the roll is successful the player is not suppressed, otherwise he falls prone and loses both actions in his next turn. If the group of players has a unit’s morale level (raging A to D) and the player risking suppression has an unobstructed view of another non-suppressed player, then he can roll a second die for morale when checking for suppression.
Example: an enemy scout attacks the player in ranged combat with an AK-74. The scout is an amateur shooter (Ranged Combat D and AGL C) and decides to up his chances by adding some ammo dice to his roll. The AK-74 has a ROF of 5, and he decides to roll 3 ammo dice.
The enemy scout rolls:
– Ranged Combat [D8+D6] = 1 SUCCESS (rolled 6 and 2)
– Ammo dice [D6+D6+D6] = 6 + 3 + 2
The scout’s fire is on target and the player is hit, with the 6 rolled on the ammo die increasing the total damage by 1.
The player risks suppression: he has to roll CUF and get at least one success. The player has CUF C, and also has line of sight over a second player, and the players’ group has a morale rating of C, so he can add a D8 to his CUF roll.
The player rolls CUF [D8+D8] = 1 SUCCESS (rolled 7 and 5)
Suppression avoided. In his next turn the player will be able to return fire or get to cover.
Finally, when pushing an attack roll, the player re-rolls all ammo dice not showing or . Any showing on the pushed roll results in a reduction of the weapon’s reliability. If it gets to 0, the weapon can no longer be employed. Two or more rolled on ammo dice mean the weapon is jammed and needs unjamming before it can resume firing.
HIT LOCATION DIE
The official TW2K dice set contains a single Hit Location Die: it’s a D6 you roll when you hit an enemy in combat (ranged or close), to see where the enemy is hit.
This is especially important when the enemy is in partial cover or wearing armor and/or a helmet.
A player can perform an aimed attack (ranged) or aimed blow (close): you pick where you want to strike but suffer a penalty on your attack roll.
AND MORE…
There’s more specific rules for melee combat, explosives, anti-tank weapons, vehicles, and all manners of non-combat activities; I’ll tackle them as their need arise while the campaign progresses.
And of course, the easiest way to learn the rules and the mechanics is to play the game.
Now that you have the basics of combat in Twilight: 2000 4th Edition, you may be interested in seeing how they’re applied in a firefight.
If that’s the case, I suggest you check these posts:
Or if you want to get the full story, you can jump to the start of this Twilight: 2000 Solo Campaign by pressing the button below.