The very short list

1. Refer to the mod DLL.
2. Create and register an IBuff singleton instance.
3. Create one (or more) BuffInstance.
4. Create IBuffTarget and IBuffEffect for the BuffInstance.
5. Process the applied BuffInstance in your mod using Singleton, BaseComponent or Harmony patch.

A bit more detailed

1. Add the mod reference to your project. The file should be at "SteamLibrary\steamapps\workshop\content\1062090\3433810580\version-0.7\BuffDebuff.dll".
   • Optionally add global using BuffDebuff as this will be the namespace for all Buff & Debuff System classes.
2. Create a singleton Buff class similar to BuffDebuffDemo.Buffs.PositiveBuff that implements IBuff. This class will declare general information about the buff, such as its name, description. It will also act as a manager and factory for the BuffInstance.
   • You can create a class from scratch or inherit from SimpleBuff, SimpleValueBuff or SimpleFloatBuff. The latter two are for buffs that create instances with a simple value.
   • If you use SimpleValueBuff or similar, you do not have enough class (BuffInstance) to provide for the generic parameters yet. Just ignore and go ahead to the next step.
   • You are not limited to one type of BuffInstance for a Buff. You can create any number of BuffInstance of any type(s) you want.

[!TIP]
BuffInstance, IBuffTarget, and IBuffEffect all have Init(), Update...() and CleanUp() methods. You can override them to add your custom logic.

1. Create a BuffInstance class similar to BuffDebuffDemo.Buffs.PositiveBuffInstance that inherit BuffInstance. This class will declare the targets and effects of the Buff.
   • You can inherit your class directly from BuffInstance or use some provided classes that support common use cases, such as BuffInstance<TValue, TBuff> or TimedBuffInstance.
   • BuffInstance must have a new() (parameterless) constructor. You then use InjectAttribute to inject necessary services into the instance similar to how you code a BaseComponent.
   • Use Init() to setup your instance. This method is called after the instance is created and injected. You would have your IBuffInstance<TBuff>.Buff and IValuedBuffInstance<TValue>.Value available at this point as well if your instance is of those types.
   • Use Update() if you need to update your instance every tick even when its Active is false. If you set Active to false, the Targets won’t be called right in that tick.
2. Create IBuffTarget(s) for your buff instance to target. This interface will define the target(s) of the buff instance.
   • You can create a class from scratch or inherit from GlobalBuffTarget and its subclasses (GlobalBeaverBuffTarget, GlobalAdultBeaverBuffTarget, GlobalChildBeaverBuffTarget, GlobalBotBuffTarget), or IdsBuffTarget.
   • Each tick, UpdateTargets() is called. If the TargetsChanged property is true, the game will use Targets as new targets and remove the buff instance from the old targets.

3. Create IBuffEffect(s) for your buff instance to apply. There is UpdateEffect() method that is called every tick if you need to.

4. Create another class (it can be a game’s singleton or a Harmony patch) that uses IBuffService to scan for your BuffInstance. Then decide what to do with the IBuffEffect(s) that they have.
   • Another way (recommended in the Step-by-step guide) is to add another BaseComponent to the entities that the buff can apply to (like BeaverSpec) and listen to the events.