MainContent.kt

@Composable
private fun MainContent(
    changeSystemBarStyle: (SystemBarStyle) -> Unit
) {
    Scaffold(
        modifier = Modifier.fillMaxSize(),
        containerColor = Color.Black
    ) { paddingValues ->

        LaunchedEffect(Unit) {
            changeSystemBarStyle(SystemBarStyle.dark(android.graphics.Color.TRANSPARENT))
        }

        val layoutDirection = LocalLayoutDirection.current
        Box(
            modifier = Modifier
                .fillMaxSize()
                .padding(
                    start = paddingValues.calculateStartPadding(layoutDirection),
                    end = paddingValues.calculateEndPadding(layoutDirection),
                    bottom = paddingValues.calculateBottomPadding(),
                )
        ) {
            Column(
                modifier = Modifier.fillMaxSize()
            ) {

                var alpha by remember {
                    mutableFloatStateOf(0f)
                }

                val color by remember(alpha) {
                    logDebug { alpha.toString() }
                    mutableStateOf(Color.Red.copy(alpha = alpha))
                }

                val animatedColor by animateColorAsState(targetValue = color, label = "")

                Spacer(
                    modifier = Modifier
                        .windowInsetsTopHeight(WindowInsets.statusBars)
                        .fillMaxWidth()
                        .background(animatedColor)
                )

                BoxWithConstraints(
                    modifier = Modifier.fillMaxSize()
                ) {

                    val minimumBoxHeight = 200.dp
                    val maximumBoxHeight = maxHeight // stop before covering the status bar
                    var boxHeight by remember {
                        mutableStateOf(minimumBoxHeight)
                    }

                    LaunchedEffect(boxHeight) {
                        alpha = (boxHeight / maximumBoxHeight).coerceIn(0f, 1f)

                    }

                    Box(
                        modifier = Modifier
                            .fillMaxWidth()
                            .height(boxHeight)
                            .background(Color.White)
                            .align(Alignment.BottomCenter)
                            .pointerInput(Unit) {
                                detectVerticalDragGestures { change, dragAmount ->
                                    if (dragAmount < 0f) { // dragging up
                                        if (boxHeight >= maximumBoxHeight) {
                                            boxHeight = maximumBoxHeight
                                        } else {
                                            if (boxHeight <= maxHeight) {
                                                boxHeight += 6.dp
                                            }
                                        }
                                    } else if (dragAmount > 0f) { // dragging down
                                        if (boxHeight <= minimumBoxHeight) {
                                            boxHeight = minimumBoxHeight
                                        } else {
                                            boxHeight -= 6.dp
                                        }
                                    }
                                }
                            }
                    ) {
                        Image(
                            painter = painterResource(id = R.drawable.cheems),
                            contentDescription = null,
                            modifier = Modifier
                                .size(boxHeight)
                                .align(Alignment.Center)
                        )
                    }
                }
            }
        }
    }
}