MainActivity.kt

@Composable
fun PlanetsScreen(...) {
    val revealPIN by viewModel.isShowingPin.collectAsStateWithLifecycle()
    val scope = rememberCoroutineScope()

    Column {
        Button(
            onClick = {
                scope.launch {
                    // Here we call a function which takes at least 10 seconds to run,
                    // directly from the main thread. Safe because the thread isn't blocked.
                    viewModel.revealPinBriefly()
                }
            }
        ) {
            Text("Reveal PIN")
        }

        if (revealPIN) {
            Text(text = "Your PIN is 1234")
        }
    }
}

MyViewModel.kt

val isShowingPin = MutableStateFlow(false)

// This function suspends the coroutine for a long time, but
// doesn't block the calling thread. So it can be called from
// the main/UI thread safely.
suspend fun revealPinBriefly() {
    isShowingPin.value = true
    delay(10_000)
    isShowingPin.value = false
}