For Medium article "The power of Android Porter/Duff Mode"

LightAnimator.kt

private var animator = ValueAnimator.ofFloat(0f, 1f).apply {
    addUpdateListener {
        val value = it.animatedValue as Float
        angle = lerp(0f, FULL_CIRCLE, value)
    }
    interpolator = CustomSpringInterpolator(INTERPOLATOR_FACTOR)
    repeatMode = ValueAnimator.RESTART
    repeatCount = ValueAnimator.INFINITE
    duration = ANIMATION_DURATION
}