Add this code to the end of the pause function to save the players new high score if one was achieved in the current play session

KotlinInvadersView.kt

val prefs = context.getSharedPreferences(
                    "Kotlin Invaders",
                    Context.MODE_PRIVATE)

    val oldHighScore = prefs.getInt("highScore", 0)

    if(highScore > oldHighScore) {
        val editor = prefs.edit()

        editor.putInt(
                "highScore", highScore)

        editor.apply()
    }