ImmersiveList.kt

@Composable
fun SampleImmersiveList(movies: List<Movie>, modifier = Modifier) {
    val selectedMovie = remember { mutableStateOf<Movie?>(movies.firstOrNull()) }

    // Container
    Box(
        modifier = Modifier
            .fillMaxWidth()
            .height(400.dp)
    ) {
        // Background
        Box(
            modifier = Modifier
                .fillMaxWidth()
                .aspectRatio(20f / 7)
                .background(selectedMovie.value?.background)
        ) {}


        // Rows
        LazyRow(
            …
        ) {
            items(movies) { movie ->
                MyMovieCard(
                    modifier = Modifier
                        .onFocusChanged {
                            if (it.hasFocus) {
                                selectedMovie.value = movie
                            }
                        },
                    …
                ) {}
            }
        }
    }
}