CountDownComposable.kt

@OptIn(ExperimentalAnimationApi::class)
@Composable
fun CountDown(
    count: Int?,
    modifier: Modifier = Modifier,
) {
    val transitionDuration = 500
    val enterTransition = scaleIn(initialScale = 1.5f, animationSpec = tween(transitionDuration))
    val exitTransition = scaleOut(targetScale = 4f, animationSpec = tween(transitionDuration)) + fadeOut(animationSpec = tween(transitionDuration))
    AnimatedVisibility(
        modifier = modifier,
        visible = count != null,
        enter = enterTransition,
        exit = exitTransition
    ) {
        val countDown = when (count) {
            0, null -> "Go"
            else -> "$count"
        }
        AnimatedContent(
            targetState = count,
            transitionSpec = { enterTransition with fadeOut(animationSpec = tween(0)) },
            contentAlignment = Alignment.Center,
        ) {
            Text(
                modifier = Modifier.padding(100.dp),
                text = countDown.uppercase(),
                color = Color.White,
                textAlign = TextAlign.Center,
            )
        }
    }
}