evennia.contrib.turnbattle.tb_magic

Simple turn-based combat system with spell casting

Contrib - Tim Ashley Jenkins 2017

This is a version of the ‘turnbattle’ contrib that includes a basic, expandable framework for a ‘magic system’, whereby players can spend a limited resource (MP) to achieve a wide variety of effects, both in and out of combat. This does not have to strictly be a system for magic - it can easily be re-flavored to any other sort of resource based mechanic, like psionic powers, special moves and stamina, and so forth.

In this system, spells are learned by name with the ‘learnspell’ command, and then used with the ‘cast’ command. Spells can be cast in or out of combat - some spells can only be cast in combat, some can only be cast outside of combat, and some can be cast any time. However, if you are in combat, you can only cast a spell on your turn, and doing so will typically use an action (as specified in the spell’s funciton).

Spells are defined at the end of the module in a database that’s a dictionary of dictionaries - each spell is matched by name to a function, along with various parameters that restrict when the spell can be used and what the spell can be cast on. Included is a small variety of spells that damage opponents and heal HP, as well as one that creates an object.

Because a spell can call any function, a spell can be made to do just about anything at all. The SPELLS dictionary at the bottom of the module even allows kwargs to be passed to the spell function, so that the same function can be re-used for multiple similar spells.

Spells in this system work on a very basic resource: MP, which is spent when casting spells and restored by resting. It shouldn’t be too difficult to modify this system to use spell slots, some physical fuel or resource, or whatever else your game requires.

To install and test, import this module’s TBMagicCharacter object into your game’s character.py module:

from evennia.contrib.turnbattle.tb_magic import TBMagicCharacter

And change your game’s character typeclass to inherit from TBMagicCharacter instead of the default:

class Character(TBMagicCharacter):

Note: If your character already existed you need to also make sure to re-run the creation hooks on it to set the needed Attributes. Use update self to try on yourself or use py to call at_object_creation() on all existing Characters.

Next, import this module into your default_cmdsets.py module:

from evennia.contrib.turnbattle import tb_magic

And add the battle command set to your default command set:

# # any commands you add below will overload the default ones. # self.add(tb_magic.BattleCmdSet())

This module is meant to be heavily expanded on, so you may want to copy it to your game’s ‘world’ folder and modify it there rather than importing it in your game and using it as-is.

evennia.contrib.turnbattle.tb_magic.ACTIONS_PER_TURN = 1

evennia.contrib.turnbattle.tb_magic.roll_init(character)

Rolls a number between 1-1000 to determine initiative.

Parameters

character (obj) – The character to determine initiative for

Returns

initiative (int) – The character’s place in initiative - higher numbers go first.

Notes

By default, does not reference the character and simply returns a random integer from 1 to 1000.

Since the character is passed to this function, you can easily reference a character’s stats to determine an initiative roll - for example, if your character has a ‘dexterity’ attribute, you can use it to give that character an advantage in turn order, like so:

return (randint(1,20)) + character.db.dexterity

This way, characters with a higher dexterity will go first more often.

evennia.contrib.turnbattle.tb_magic.get_attack(attacker, defender)

Returns a value for an attack roll.

Parameters

• attacker (obj) – Character doing the attacking

• defender (obj) – Character being attacked

Returns

attack_value (int) –

Attack roll value, compared against a defense value

to determine whether an attack hits or misses.

Notes

By default, returns a random integer from 1 to 100 without using any properties from either the attacker or defender.

This can easily be expanded to return a value based on characters stats, equipment, and abilities. This is why the attacker and defender are passed to this function, even though nothing from either one are used in this example.

evennia.contrib.turnbattle.tb_magic.get_defense(attacker, defender)

Returns a value for defense, which an attack roll must equal or exceed in order for an attack to hit.

Parameters

• attacker (obj) – Character doing the attacking

• defender (obj) – Character being attacked

Returns

defense_value (int) –

Defense value, compared against an attack roll

to determine whether an attack hits or misses.

Notes

By default, returns 50, not taking any properties of the defender or attacker into account.

As above, this can be expanded upon based on character stats and equipment.

evennia.contrib.turnbattle.tb_magic.get_damage(attacker, defender)

Returns a value for damage to be deducted from the defender’s HP after abilities successful hit.

Parameters

• attacker (obj) – Character doing the attacking

• defender (obj) – Character being damaged

Returns

damage_value (int) –

Damage value, which is to be deducted from the defending

character’s HP.

Notes

By default, returns a random integer from 15 to 25 without using any properties from either the attacker or defender.

Again, this can be expanded upon.

evennia.contrib.turnbattle.tb_magic.apply_damage(defender, damage)

Applies damage to a target, reducing their HP by the damage amount to a minimum of 0.

Parameters

• defender (obj) – Character taking damage

• damage (int) – Amount of damage being taken

evennia.contrib.turnbattle.tb_magic.at_defeat(defeated)

Announces the defeat of a fighter in combat.

Parameters

defeated (obj) – Fighter that’s been defeated.

Notes

All this does is announce a defeat message by default, but if you want anything else to happen to defeated fighters (like putting them into a dying state or something similar) then this is the place to do it.

evennia.contrib.turnbattle.tb_magic.resolve_attack(attacker, defender, attack_value=None, defense_value=None)

Resolves an attack and outputs the result.

Parameters

• attacker (obj) – Character doing the attacking

• defender (obj) – Character being attacked

Notes

Even though the attack and defense values are calculated extremely simply, they are separated out into their own functions so that they are easier to expand upon.

evennia.contrib.turnbattle.tb_magic.combat_cleanup(character)

Cleans up all the temporary combat-related attributes on a character.

Parameters

character (obj) – Character to have their combat attributes removed

Notes

Any attribute whose key begins with ‘combat_’ is temporary and no longer needed once a fight ends.

evennia.contrib.turnbattle.tb_magic.is_in_combat(character)

Returns true if the given character is in combat.

Parameters

character (obj) – Character to determine if is in combat or not

Returns

(bool) – True if in combat or False if not in combat

evennia.contrib.turnbattle.tb_magic.is_turn(character)

Returns true if it’s currently the given character’s turn in combat.

Parameters

character (obj) – Character to determine if it is their turn or not

Returns

(bool) – True if it is their turn or False otherwise

evennia.contrib.turnbattle.tb_magic.spend_action(character, actions, action_name=None)

Spends a character’s available combat actions and checks for end of turn.

Parameters

• character (obj) – Character spending the action

• actions (int) – Number of actions to spend, or ‘all’ to spend all actions

Keyword Arguments

• action_name (str or None) – If a string is given, sets character’s last action in

• to provided string (combat) –

class evennia.contrib.turnbattle.tb_magic.TBMagicCharacter(*args, **kwargs)

Bases: evennia.objects.objects.DefaultCharacter

A character able to participate in turn-based combat. Has attributes for current and maximum HP, and access to combat commands.

at_object_creation()

Called once, when this object is first created. This is the normal hook to overload for most object types.

Adds attributes for a character’s current and maximum HP. We’re just going to set this value at ‘100’ by default.

You may want to expand this to include various ‘stats’ that can be changed at creation and factor into combat calculations.

at_before_move(destination)

Called just before starting to move this object to destination.

Parameters

destination (Object) – The object we are moving to

Returns

shouldmove (bool) – If we should move or not.

Notes

If this method returns False/None, the move is cancelled before it is even started.

exception DoesNotExist

Bases: evennia.objects.objects.DefaultCharacter.DoesNotExist

exception MultipleObjectsReturned

Bases: evennia.objects.objects.DefaultCharacter.MultipleObjectsReturned

path = 'evennia.contrib.turnbattle.tb_magic.TBMagicCharacter'

typename = 'TBMagicCharacter'

class evennia.contrib.turnbattle.tb_magic.TBMagicTurnHandler(*args, **kwargs)

Bases: evennia.scripts.scripts.DefaultScript

This is the script that handles the progression of combat through turns. On creation (when a fight is started) it adds all combat-ready characters to its roster and then sorts them into a turn order. There can only be one fight going on in a single room at a time, so the script is assigned to a room as its object.

Fights persist until only one participant is left with any HP or all remaining participants choose to end the combat with the ‘disengage’ command.

at_script_creation()

Called once, when the script is created.

at_stop()

Called at script termination.

at_repeat()

Called once every self.interval seconds.

initialize_for_combat(character)

Prepares a character for combat when starting or entering a fight.

Parameters

character (obj) – Character to initialize for combat.

start_turn(character)

Readies a character for the start of their turn by replenishing their available actions and notifying them that their turn has come up.

Parameters

character (obj) – Character to be readied.

Notes

Here, you only get one action per turn, but you might want to allow more than one per turn, or even grant a number of actions based on a character’s attributes. You can even add multiple different kinds of actions, I.E. actions separated for movement, by adding “character.db.combat_movesleft = 3” or something similar.

next_turn()

Advances to the next character in the turn order.

turn_end_check(character)

Tests to see if a character’s turn is over, and cycles to the next turn if it is.

Parameters

character (obj) – Character to test for end of turn

join_fight(character)

Adds a new character to a fight already in progress.

Parameters

character (obj) – Character to be added to the fight.

exception DoesNotExist

Bases: evennia.scripts.scripts.DefaultScript.DoesNotExist

exception MultipleObjectsReturned

Bases: evennia.scripts.scripts.DefaultScript.MultipleObjectsReturned

path = 'evennia.contrib.turnbattle.tb_magic.TBMagicTurnHandler'

typename = 'TBMagicTurnHandler'

class evennia.contrib.turnbattle.tb_magic.CmdFight(**kwargs)

Bases: evennia.commands.command.Command

Starts a fight with everyone in the same room as you.

Usage:

fight

When you start a fight, everyone in the room who is able to fight is added to combat, and a turn order is randomly rolled. When it’s your turn, you can attack other characters.

key = 'fight'

help_category = 'combat'

func()

This performs the actual command.

aliases = []

lock_storage = 'cmd:all();'

class evennia.contrib.turnbattle.tb_magic.CmdAttack(**kwargs)

Bases: evennia.commands.command.Command

Attacks another character.

Usage:

attack <target>

When in a fight, you may attack another character. The attack has a chance to hit, and if successful, will deal damage.

key = 'attack'

help_category = 'combat'

func()

This performs the actual command.

aliases = []

lock_storage = 'cmd:all();'

class evennia.contrib.turnbattle.tb_magic.CmdPass(**kwargs)

Bases: evennia.commands.command.Command

Passes on your turn.

Usage:

pass

When in a fight, you can use this command to end your turn early, even if there are still any actions you can take.

key = 'pass'

aliases = ['hold', 'wait']

help_category = 'combat'

func()

This performs the actual command.

lock_storage = 'cmd:all();'

class evennia.contrib.turnbattle.tb_magic.CmdDisengage(**kwargs)

Bases: evennia.commands.command.Command

Passes your turn and attempts to end combat.

Usage:

disengage

Ends your turn early and signals that you’re trying to end the fight. If all participants in a fight disengage, the fight ends.

key = 'disengage'

aliases = ['spare']

help_category = 'combat'

func()

This performs the actual command.

lock_storage = 'cmd:all();'

class evennia.contrib.turnbattle.tb_magic.CmdLearnSpell(**kwargs)

Bases: evennia.commands.command.Command

Learn a magic spell.

Usage:

learnspell <spell name>

Adds a spell by name to your list of spells known.

The following spells are provided as examples:

|wmagic missile|n (3 MP): Fires three missiles that never miss. Can target

up to three different enemies.

|wflame shot|n (3 MP): Shoots a high-damage jet of flame at one target.

|wcure wounds|n (5 MP): Heals damage on one target.

|wmass cure wounds|n (10 MP): Like ‘cure wounds’, but can heal up to 5

targets at once.

|wfull heal|n (12 MP): Heals one target back to full HP.

|wcactus conjuration|n (2 MP): Creates a cactus.

key = 'learnspell'

help_category = 'magic'

func()

This performs the actual command.

aliases = []

lock_storage = 'cmd:all();'

class evennia.contrib.turnbattle.tb_magic.CmdCast(**kwargs)

Bases: evennia.commands.default.muxcommand.MuxCommand

Cast a magic spell that you know, provided you have the MP to spend on its casting.

Usage:

cast <spellname> [= <target1>, <target2>, etc…]

Some spells can be cast on multiple targets, some can be cast on only yourself, and some don’t need a target specified at all. Typing ‘cast’ by itself will give you a list of spells you know.

key = 'cast'

help_category = 'magic'

func()

This performs the actual command.

Note: This is a quite long command, since it has to cope with all the different circumstances in which you may or may not be able to cast a spell. None of the spell’s effects are handled by the command - all the command does is verify that the player’s input is valid for the spell being cast and then call the spell’s function.

aliases = []

lock_storage = 'cmd:all();'

class evennia.contrib.turnbattle.tb_magic.CmdRest(**kwargs)

Bases: evennia.commands.command.Command

Recovers damage and restores MP.

Usage:

rest

Resting recovers your HP and MP to their maximum, but you can only rest if you’re not in a fight.

key = 'rest'

help_category = 'combat'

func()

This performs the actual command.

aliases = []

lock_storage = 'cmd:all();'

class evennia.contrib.turnbattle.tb_magic.CmdStatus(**kwargs)

Bases: evennia.commands.command.Command

Gives combat information.

Usage:

status

Shows your current and maximum HP and your distance from other targets in combat.

key = 'status'

help_category = 'combat'

func()

This performs the actual command.

aliases = []

lock_storage = 'cmd:all();'

class evennia.contrib.turnbattle.tb_magic.CmdCombatHelp(**kwargs)

Bases: evennia.commands.default.help.CmdHelp

View help or a list of topics

Usage:

help <topic or command> help list help all

This will search for help on commands and other topics related to the game.

func()

Run the dynamic help entry creator.

aliases = ['?']

help_category = 'general'

key = 'help'

lock_storage = 'cmd:all()'

class evennia.contrib.turnbattle.tb_magic.BattleCmdSet(cmdsetobj=None, key=None)

Bases: evennia.commands.default.cmdset_character.CharacterCmdSet

This command set includes all the commmands used in the battle system.

key = 'DefaultCharacter'

at_cmdset_creation()

Populates the cmdset

path = 'evennia.contrib.turnbattle.tb_magic.BattleCmdSet'

evennia.contrib.turnbattle.tb_magic.spell_healing(caster, spell_name, targets, cost, **kwargs)

Spell that restores HP to a target or targets.

kwargs:

healing_range (tuple): Minimum and maximum amount healed to

each target. (20, 40) by default.

evennia.contrib.turnbattle.tb_magic.spell_attack(caster, spell_name, targets, cost, **kwargs)

Spell that deals damage in combat. Similar to resolve_attack.

kwargs:

attack_name (tuple): Single and plural describing the sort of

attack or projectile that strikes each enemy.

damage_range (tuple): Minimum and maximum damage dealt by the

spell. (10, 20) by default.

accuracy (int): Modifier to the spell’s attack roll, determining

an increased or decreased chance to hit. 0 by default.

attack_count (int): How many individual attacks are made as part

of the spell. If the number of attacks exceeds the number of targets, the first target specified will be attacked more than once. Just 1 by default - if the attack_count is less than the number targets given, each target will only be attacked once.

evennia.contrib.turnbattle.tb_magic.spell_conjure(caster, spell_name, targets, cost, **kwargs)

Spell that creates an object.

kwargs:

obj_key (str): Key of the created object. obj_desc (str): Desc of the created object. obj_typeclass (str): Typeclass path of the object.

If you want to make more use of this particular spell funciton, you may want to modify it to use the spawner (in evennia.utils.spawner) instead of creating objects directly.