# Animating Particle Properties Across Disparate Values

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Supply keyframe sequences to do linear or nonlinear particle animations.

### Overview

An `SKKeyframeSequence` object enables you to specify multiple values for an emitter node's properties over a specific time period. The property values you choose may be arbitrary, which results in your ability to graph those property changes linearly or nonlinearly over time.

When you use a sequence, the values are not randomized. Instead, the sequence specifies all of the values of the property. Each keyframe value includes a value object and a timestamp. The timestamps are specified in a range from 0 to 1.0, where 0 represents the birth of the particle and 1.0 represents its death.

The properties for which `SKEmitterNode` offers a keyframe sequence are:

|Property|Specifies|Example use|
|--------|---------|-----------|
|`particleColorSequence`|A sequence of arbitrary colors a particle should reflect over its lifetime.|Embers from a fire might specify the color sequence (white, yellow, orange, and brown) to appear hot, and then cool.|
|`particleColorBlendFactorSequence`|A sequence of color blend factors a particle should apply over its lifetime.|Embers from a fire might specify the color blend factor sequence (0, 1, 0, 1, ... etc.) to simulate flickering.|
|`particleScaleSequence`|A sequence of sizes of a particle over its lifetime.|Balloons might use the scale sequence (0.1, 1, 1, 1, 0.1) to simulate inflation, and flying for some time before deflating.|
|`particleAlphaSequence`|A sequence of levels of transparency a particle undergoes over its lifetime.|Fireflies might specify a disparate sequence of alpha values to simulate random lighting patterns as they travel.|

The following code demonstrates using `particleScaleSequence` to animate the scale of an emitter node's particles over their lifetime. Initially, the particles' scale is 0.2 and then increases to 0.7 one-quarter of the way through the sequence. Three-quarters of the way through the sequence, the scale reaches its minimum size, 0.1. It remains at this size until it dies.

```swift
let scaleSequence = SKKeyframeSequence(keyframeValues: [0.2, 0.7, 0.1],
                                       times: [0.0, 0.250, 0.75])
myEmitter.particleScaleSequence = scaleSequence
```

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