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# loops

A Boolean value that determines whether the system repeats its emission and idle periods.

```
var loops: Bool { get set }
```

## Discussion

If this value is <doc://com.apple.documentation/documentation/Swift/true> (the default), you can make the system emit particles periodically or sporadically. For example, in a looping system where the [`emissionDuration`](/documentation/SceneKit/SCNParticleSystem/emissionDuration) value is `1.0` seconds and the [`idleDuration`](/documentation/SceneKit/SCNParticleSystem/idleDuration) value is `1.0` seconds, the system alternates alternates between equal one-second periods of spawning and not spawning particles. Use the [`emissionDurationVariation`](/documentation/SceneKit/SCNParticleSystem/emissionDurationVariation) and [`idleDurationVariation`](/documentation/SceneKit/SCNParticleSystem/idleDurationVariation) properties to randomize the duration of each emission and idle period, making the emission behavior more sporadic.

Specify <doc://com.apple.documentation/documentation/Swift/false> for particle systems that create one-shot effects, such as an explosion that appears when a game character is defeated.

---

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