Unify KMPKotlin Multiplatform 跨平台开发框架

@Composable
fun HelloWorldApp() {
    var count by remember { mutableIntStateOf(0) }
    
    MaterialTheme {
        Column(
            modifier = Modifier
                .fillMaxSize()
                .padding(16.dp),
            horizontalAlignment = Alignment.CenterHorizontally,
            verticalArrangement = Arrangement.spacedBy(16.dp)
        ) {
            Card {
                Column(
                    modifier = Modifier.padding(16.dp),
                    horizontalAlignment = Alignment.CenterHorizontally
                ) {
                    Text(
                        text = "🚀 Unify-Core",
                        style = MaterialTheme.typography.headlineMedium,
                        color = MaterialTheme.colorScheme.primary
                    )
                    Text(
                        text = "Kotlin Multiplatform Compose 框架",
                        style = MaterialTheme.typography.bodyMedium
                    )
                }
            }
            
            Card {
                Column(
                    modifier = Modifier.padding(16.dp),
                    horizontalAlignment = Alignment.CenterHorizontally
                ) {
                    Text(
                        text = "计数: $count",
                        style = MaterialTheme.typography.headlineLarge
                    )
                    
                    Button(
                        onClick = { count++ }
                    ) {
                        Text("增加")
                    }
                }
            }
            
            Card {
                Column(
                    modifier = Modifier.padding(16.dp)
                ) {
                    Text(
                        text = "平台信息",
                        style = MaterialTheme.typography.titleMedium
                    )
                    Text("平台: ${getPlatformName()}")
                }
            }
        }
    }
}

// 共享代码 (commonMain)
expect fun getPlatformName(): String

// Android 实现 (androidMain)
actual fun getPlatformName(): String = 
    "Android ${Build.VERSION.RELEASE} (API ${Build.VERSION.SDK_INT})"

// iOS 实现 (iosMain)
actual fun getPlatformName(): String {
    val device = UIDevice.currentDevice
    return "iOS ${device.systemName} ${device.systemVersion}"
}

// Web 实现 (jsMain)
actual fun getPlatformName(): String = "Web (${js("navigator.userAgent")})"