### StyleStateKeySample
```kotlin
@Composable
fun StyleStateKeySample() {
    // Create a new StyleStateKey
    val playingStateKey = StyleStateKey(false)
    // Introduce an extension function to read the style state
    fun StyleScope.playerPlaying(value: Style) {
        state(playingStateKey, value) { key, state -> state[key] }
    }
    // Using the extension function to change the border color to green while playing
    val style = Style {
        borderColor(Color.Gray)
        playerPlaying { borderColor(Color.Green) }
    }
    // Using the style in a composable that sets the state.
    MediaPlayer(url = "https://example.com/media/video", style = style)
}
```