val spotlight = Spotlight.Builder(this)
    .setTargets(firstTarget, secondTarget, thirdTarget ...)
    .setBackgroundColor(R.color.spotlightBackground)
    .setDuration(1000L)
    .setAnimation(DecelerateInterpolator(2f))
    .setContainer(viewGroup)
    .setOnSpotlightListener(object : OnSpotlightListener {
      override fun onStarted() {
        Toast.makeText(this@MainActivity, "spotlight is started", Toast.LENGTH_SHORT).show()
      }
      override fun onEnded() {
        Toast.makeText(this@MainActivity, "spotlight is ended", Toast.LENGTH_SHORT).show()
      }
    })
    .build()         

// with core-ktx method.
view.doOnPreDraw { Spotlight.Builder(this)...start() }

val target = Target.Builder()
    .setAnchor(100f, 100f)
    .setShape(Circle(100f))
    .setEffect(RippleEffect(100f, 200f, argb(30, 124, 255, 90)))
    .setOverlay(layout)
    .setOnTargetListener(object : OnTargetListener {
      override fun onStarted() {
        makeText(this@MainActivity, "first target is started", LENGTH_SHORT).show()
      }
      override fun onEnded() {
        makeText(this@MainActivity, "first target is ended", LENGTH_SHORT).show()
      }
    })
    .build()

val spotlight = Spotlight.Builder(this)...start()

spotlight.finish()

val spotlight = Spotlight.Builder(this)...start()

spotlight.next()

spotlight.previous()

spotlight.show(2)

class CustomShape(
    override val duration: Long,
    override val interpolator: TimeInterpolator
) : Shape {

  override fun draw(canvas: Canvas, point: PointF, value: Float, paint: Paint) {
    // draw your shape here.
  }
}

class CustomEffect(
    override val duration: Long,
    override val interpolator: TimeInterpolator,
    override val repeatMode: Int
) : Effect {

  override fun draw(canvas: Canvas, point: PointF, value: Float, paint: Paint) {
    // draw your effect here.
  }
}