Starting fights

Kicking kobolds is fun. Let’s make it so you can kick them to death!

Getting healthy

1. Navigate to modules/game/components

2. Create a new file named health.lua

--- @class Health : Component
--- @field maxHP integer
--- @field hp integer
--- @overload fun(hp: integer): Health
local Health = prism.Component:extend("Health")

function Health:__new(maxHP)
   self.maxHP = maxHP
   self.hp = maxHP
end

return Health

In kobold.lua, add our new Health component to the list.

prism.components.Health(3),

Implementing the die action

Next we’ll create a Die action to encapsulate the removal of actors. Create a file called modules/game/actions/die.lua and enter the following:

---@class Die : Action
---@overload fun(owner: Actor): Die
local Die = prism.Action:extend("Die")

function Die:perform(level)
   level:removeActor(self.owner)
end

return Die

Now that we have the Die action, let’s test it by changing the Fall action to use it instead of just removing the actor from the level.

Navigate to modules/game/actions/fall.lua and replace the single line in its perform with the following:

- level:removeActor(self.owner) -- into the depths with you!

level:perform(prism.actions.Die(self.owner))

Doing damage

Next we’re going to add the Damage action. This accepts a single target: the amount of damage to be taken. It modifies the health of the target and if it’s at or below zero we trigger the Die action we just added.

An action’s targets are the parameters passed into the perform method, in order. We use the Target to apply validation to ensure types within perform match our expectations. Typically, you will be passing in instances of actors, but in this case it’s just a number representing the amount of damage we will apply.

local DamageTarget = prism.Target():isType("number")

--- @class Damage : Action
--- @overload fun(owner: Actor, damage: number): Damage
local Damage = prism.Action:extend("Damage")
Damage.targets = { DamageTarget }
Damage.requiredComponents = { prism.components.Health }

function Damage:perform(level, damage)
   local health = self.owner:expect(prism.components.Health)
   health.hp = health.hp - damage

   if health.hp <= 0 then
      level:perform(prism.actions.Die(self.owner))
   end
end

return Damage

Let’s head back to modules/game/actions/kick.lua and at the end of Kick:perform we’re going to add the following:

function Kick:perform(level, kicked)
   ...

   local damage = prism.actions.Damage(kicked, 1)
   level:tryPerform(damage)
end

That’s all for now

We’ve started on a basic health system and made our Kick action deal damage. In the next chapter we’ll implement player health, make kobolds dangerous by giving them the attack action, and implement the required logic for player death.