Sealed class

SealedClass.kt

sealed class Screen {
    abstract val screenName: String

    object Menu : Screen() {
        override val screenName = "Menu screen"
    }

    object Leaderboard : Screen() {
        override val screenName = "Leaderboard screen"
    }

    sealed class Game(var score: Int) : Screen() {
        class Level1(score: Int) : Game(score) {
            override val screenName = "Level 1"
        }

        class Level2(score: Int) : Game(score) {
            override val screenName = "Level 2"
        }

        class Level3(score: Int) : Game(score) {
            override val screenName = "Level 3"
        }
    }
}