Sequence System

Build gameplay presentation flows as declarative step lists instead of deeply nested coroutines.

Structure

SequenceAsset (ScriptableObject)
  [SerializeReference] List<SequenceStep>

SequenceRunner (MonoBehaviour)
  - Runs steps in order as coroutines

SequenceStep (abstract, [Serializable])
  - Base class for custom steps

Built-In Steps

Step	Description
WaitStep	Waits for N seconds
MoveStep	Moves a Transform to a destination with easing
FadeStep	Animates CanvasGroup alpha
ScaleStep	Animates Transform scale
SoundStep	Plays an AudioClip
CallbackStep	Invokes a UnityEvent

Quick Start

Option A: SequenceAsset

Create -> AchUtils/Sequence/Sequence Asset

Add steps in the inspector, then run the asset:

using AchUtils.Sequence;

[SerializeField] SequenceAsset introSequence;
[SerializeField] SequenceRunner runner;

void PlayIntro()
{
    runner.Run(introSequence);
}

Option B: Build in Code

var steps = new List<SequenceStep>
{
    new FadeStep  { Target = overlay,    TargetAlpha = 1f, Duration = 0.3f },
    new WaitStep  { Duration = 0.5f },
    new MoveStep  { Target = boss,       Destination = centerPos, Duration = 1f },
    new ScaleStep { Target = boss,       TargetScale = Vector3.one * 1.5f, Duration = 0.3f },
    new SoundStep { Clip = bossRoar },
    new FadeStep  { Target = overlay,    TargetAlpha = 0f, Duration = 0.5f },
};

runner.Run(steps);

API

SequenceRunner

void Run(SequenceAsset asset)
void Run(IEnumerable<SequenceStep> steps)
void Stop()

bool IsRunning

event Action OnCompleted
event Action OnStopped

MoveStep

Transform       Target
Vector3         Destination
float           Duration
AnimationCurve  Ease
bool            UseLocalSpace

FadeStep

CanvasGroup     Target
float           TargetAlpha
float           Duration
AnimationCurve  Ease

ScaleStep

Transform       Target
Vector3         TargetScale
float           Duration
AnimationCurve  Ease

SoundStep

AudioClip       Clip
float           Volume
bool            WaitUntilFinished

SoundStep plays the clip at the SequenceRunner position and does not depend on Camera.main.

CallbackStep

UnityEvent      OnExecute

Custom Steps

[Serializable]
public class ShowPanelStep : SequenceStep
{
    public GameObject Panel;
    public float HoldDuration = 2f;

    public override IEnumerator Execute(SequenceRunner runner)
    {
        Panel.SetActive(true);
        yield return new WaitForSeconds(HoldDuration);
        Panel.SetActive(false);
    }
}

Add [Serializable] so the type can be selected through [SerializeReference].

Completion Event

runner.OnCompleted += () =>
{
    Debug.Log("Intro sequence completed");
    StartGameplay();
};

runner.Run(introSequence);

Boss Intro Example

FadeStep     Overlay fade in
WaitStep     Wait 0.5s
MoveStep     Boss enters
ScaleStep    Boss scales up
SoundStep    Boss roar
FadeStep     Overlay fade out
CallbackStep Show UI