Effect Lifecycle & Tick System

Designing an Effect’s Lifecycle

Each ActiveEffect has a clear lifecycle: applied → updated every frame → expires → removed. Notably, the system handles two distinct types of effects:

  • Persistent effects (Slow, Stun): Take effect immediately upon application and persist for their duration — no tick needed
  • Periodic effects (Burn, Poison): Deal damage every N seconds — require a separate tick timer
// ActiveEffect.cs — returns true when it's time to apply damage
public bool UpdateTick(float deltaTime)
{
    RemainingTime -= deltaTime;

    if (TickInterval <= 0) return false; // Slow/Stun: no ticking

    _currentTickTimer -= deltaTime;
    if (_currentTickTimer <= 0)
    {
        _currentTickTimer += TickInterval; // Reset cycle
        return true; // Signal: "Time to deal damage!"
    }
    return false;
}

Preventing Effect Stacking

If the same tower fires repeatedly, dozens of ActiveEffect instances should not pile up. The system checks and only refreshes the duration if the same source and same effect type already exists:

// Enemy.cs
public void AddEffect(ActiveEffect effect)
{
    foreach (var existing in _activeEffects)
    {
        if (existing.SourceId == effect.SourceId && existing.EffectType == effect.EffectType)
        {
            existing.SetRemainingTime(effect.RemainingTime); // Refresh, don't stack
            return;
        }
    }
    _activeEffects.Add(effect);
    RecalculateStats(); // Recalculate speed and stun after every change
}

Immediate Stat Recalculation

When effects change, RecalculateStats() runs immediately to update SpeedModifier and IsStunned:

private void RecalculateStats()
{
    SpeedModifier = 1f;
    IsStunned = false;

    foreach (var effect in _activeEffects)
    {
        IsStunned |= effect.IsStunning();
        SpeedModifier -= effect.GetSpeedReduction();
    }

    // Stun override: speed = 0; Slow minimum cap: never slower than 10%
    if (IsStunned) SpeedModifier = 0f;
    else if (SpeedModifier < 0.1f) SpeedModifier = 0.1f;
}

EnemyView reads CurrentSpeed = BaseSpeed × SpeedModifier to sync animation speed — this is why the walk animation visibly slows when an enemy is hit by an Ice tower.