FS3 Code Roadmap

  • [code]
  • [fs3]
  • [chargen]

Whether you’re modifying FS3 for your own house rules or using it as a pattern for your own skill system, it may help you to understand the key code blocks that make up the FS3 codebase.

FS3 Plugins

FS3 is implemented as two plugins: FS3Skills (including luck and XP) and FS3Combat. The combat plugin is separate so it can be easily disabled in games that don’t want automated combat.

FS3 Skills

This section describes some important components of the FS3 Skills plugin.

Database Models

The FS3 code uses custom database models to store its data. It could store everything as simple hashes on the Character object, but the FS3 ability types have a number of properties: name, rating, XP spent, etc. Having database models makes it easier to access those various fields individualy. All of the FS3 data models use references to connect them to the character:

class FS3Attribute < Ohm::Model
  reference :character, "AresMUSH::Character"
  attribute :name
  attribute :rating, :type => DataType::Integer, :default => 0
class FS3ActionSkill < Ohm::Model
  reference :character, "AresMUSH::Character"
  attribute :name
  attribute :rating, :type => DataType::Integer, :default => 0
class Character < Ohm::Model
  collection :fs3_attributes, "AresMUSH::FS3Attribute"
  collection :fs3_action_skills, "AresMUSH::FS3ActionSkill"


FS3 is designed to be configured for individual games without needing to modify the code, so a lot of stuff is controlled by the configuration files. The ability lists, chargen limits, starting skills, XP costs, and more are all set in the configuration files. These are described in detail in Configuring FS3 Skills.


FS3 has a slew of shared helper methods, in separate files organized by topic: rolls, chargen, xp, etc. The helpers actually contain the meat of the system. Most of the commands are actually prety bare-bones, doing little more than parsing args and calling helpers.

Ability Types

A lot of FS3 behaves differently for the different ability types. For example, the code to set an ability generates a different database model for each type:

In `plugins/fs3skills/helpers/chargen.rb`:
def self.set_ability(client, char, ability_name, rating)
  case ability_type
  when :action
    ability = FS3ActionSkill.create(character: char, name: ability_name, rating: rating)
  when :background
    ability = FS3BackgroundSkill.create(character: char, name: ability_name, rating: rating)

This is an important consideration if you were thinking about expanding FS3 for things like powers or another class of skill. It’s really not designed for that, and it’s going to be a real pain to do.

Roll Parameters

An important utility class in the skills plugin is RollParams. This method encapsulates the parameters that go into a roll: ability name, linked attribute and modifier.

Typically this will be built from the parse_roll_params method, which cracks apart strings like roll Firearms and roll Firearms+Brawn-2.

FS3 Combat

This section describes some key components of the FS3 Combat plugin.

Combat Messages

Most emits are sent to everyone in the combat.

FS3Combat.emit_to_combat(combat, message, npcmaster_text)

If a command can be executed by another player (common for NPCs, but sometimes used to take actions when someone is idle), you want to be sure to supply the “NPC Master Text”. This is what generates the text at the end saying who did the command. For example:

 <FS3Combat> Bob will reload this turn. (by Faraday)

NPC Master Text can be generated automatically using the helper:

FS3Combat.npcmaster_text(character_or_npc_name, enactor)

Less commonly, you might want to emit only to the combat organizer (like when secret modifiers are applied) or to an individual combatant:

FS3Combat.emit_to_organizer(combat, message, npcmaster_text)
FS3Combat.emit_to_combatant(combatant, message)

Database Models

Like the skills plugin, combat has its own set of database models. The two at the core are Combat - representing a combat instance - and Combatant - representing someone involved in a combat.

The Combatant class can reference either a character object (for a PC or ‘named’ NPC) or a virtual NPC object that will be recycled when the combat is over. It stores all the combat-specific information like ammunition, gear, action and stance. Information that persists when a combat is over, like damage, has its own separate model.


The combat system is fully configurable, so it has a bunch of configuration files for everything from gear to hit locations. These are described in detail in Configuring FS3 Combat.


Again, like the skills system, much of combat is encapsulated in short, focused helper methods: roll_defense, attack_target, determine_cover, determine_damage, weapon_defense_skill, etc. The commands are mostly lightweight wrappers for the helpers.


All combat actions have a corresponding class that inherits from the CombatAction class. The base CombatAction class provides some helpful utilities for parsing targets and some utility attributes like combatant and name.

Each action must implement several methods:

  • prepare - Parses the action arguments, does error checking, and stores information in action-specific attributes. May return an error message if there’s a problem. This will be emitted to the player.
  • print_action - Prints the intended action in future tense, like: “Faraday will attack Bob this turn.”
  • print_action_short - Prints the intended action in a short format suitable for the combat HUD.
  • resolve - Resolves the attack when a new turn is triggered. Does damage, updates ammo, imposes penalties, or whatever other effects the action has. Returns an array of messages with the results of the action. These will be emitted to the combat.

Action Example

The aim action is a good example to look at to see how this all works.

First is the class definition - notice that it inherits from CombatAction so it has access to all the action utilities.

class AimAction < CombatAction

Next is the prepare method. Aim has only a single argument - the target name. It can use the standard parse_targets utility of the CombatAction to turn a string like “Bob Joe” into a list of combatants representing the targets. There’s also an error check to ensure that you only specify one combatant when aiming.

  def prepare
    error = parse_targets(self.action_args)
    return error if error
    return t('fs3combat.only_one_target') if (self.targets.count > 1)
    return nil

Notice that, like command error-checkers, prepare can either return an error message (if something is wrong) or nil (if everything is OK).

The two print action methods are pretty straightforward; they just return a message like “Faraday will aim at Bob” or “Aim Bob”. Note that even though we know we only have one target, we can still use the print_target_names utility from the base class to get a string with the name.

  def print_action
    msg = t('fs3combat.aim_action_msg_long', :name => self.name, :target => self.print_target_names)
  def print_action_short
    t('fs3combat.aim_action_msg_short', :name => self.name, :target => self.print_target_names)

Last is the resolve method. Aim is interesting because it doesn’t actually do anything immediately. It’s a preparatory action that saves who the character is aiming at. The resolution message is simply “Faraday aims at Bob.”

  def resolve
    self.combatant.update(aim_target: self.target)
    [t('fs3combat.aim_resolution_msg', :name => self.name, :target => self.print_target_names)]

So where does the aim actually take effect? Like many combat properties, it is used in various helper methods. Specifically, when determining whether an attack hits (in FS3Combat.roll_attack), it does this:

  aiming_mod = (combatant.is_aiming? && (combatant.aim_target == combatant.action.target)) ? 3 : 0

If the combatant is aiming and hasn’t changed targets since they aimed, give them a +3 modifier.

Other types of actions may initiate attacks (using FS3Combat.attack_target), trigger a recovery check (using FS3Combat.check_for_unko), or update other combat properties (like reloading, which uses combatant.update(ammo: combatant.max_ammo)).

Finally, it’s worth noting that many combat properties get reset at the end of a turn. The aim target, for instance, is cleared if you end a turn with an action other than ‘aim’ set. This is all handled in the FS3Combat.reset_for_new_turn method.

Custom Hooks

There are two places in the combat code where you can hook in your custom changes without touching the main code and potentially running into merge conflicts.

  • Combat Actions - Adding new combat actions to FS3.
  • New Turn Triggers - Actions to be taken at the end of each turn, like resetting flags or handling special kinds of damage.

Web Portal

One of the really nice selling points of Ares is the web portal, so you’ll want to consider having a web-based chargen for your system. FS3 has several web components.

Character Creation Abilities Tab

Much of the web chargen is generic - demographics, background, groups, etc. The FS3 bits are centered in the Abilities tab. The FS3Skills::ChargenCharRequestHandler provides information driving this screen, representing the character’s current abilities and specialties in hash form. FS3Skills::ChargenInfoRequestHandler specifies the general information about what abilities are available and what skill limits are in effect.

On the Ember side, the chargen.js controller has a lot of logic to perform some client-side error checking. This is not strictly necessary; everything will be fully error-checked by the server on the review screen. But having the most commonly-encountered errors client-side makes a much more pleasant experience for the players.

Several Ember Components encapsulate the display and controls for modifying a single ability. For example, the fs3-actionbox component includes everything needed for one of the action skill rows:

Profile Tab

The fs3-sheet and fs3-damage components are used on the character profile system tab to show simple lists of the character’s skills and any damage taken.