Simple Tic Tac Toe Game between two players

Board.kt

enum class Player { 
    X, O
}

class Board {
    private val slots = "1,2,3,4,5,6,7,8,9".split(",").toTypedArray()
    
    fun show() { 
        for ((index, item) in slots.withIndex()) {
            print(item)

            if (index == 2 || index == 5) {
                println()
                println("——————————")
            } else if (index < 2 || index < 5 || index < 8) 
                print(" | ")
        }
    }
    
    fun isPlayerWinner(player: Player): Boolean {
        return (slots[0] == player.name && slots[1] == player.name && slots[2] == player.name) || // top row
                (slots[3] == player.name && slots[4] == player.name && slots[5] == player.name) || // middle row
                (slots[6] == player.name && slots[7] == player.name && slots[8] == player.name) || // bottom row

                // diagonals
                (slots[0] == player.name && slots[4] == player.name && slots[8] == player.name) ||
                (slots[2] == player.name && slots[4] == player.name && slots[6] == player.name) ||

                // columns
                (slots[0] == player.name && slots[3] == player.name && slots[6] == player.name) ||
                (slots[1] == player.name && slots[4] == player.name && slots[7] == player.name) ||
                (slots[2] == player.name && slots[5] == player.name && slots[8] == player.name)
    }


    fun insertPlayerMove(player: Player, selectedSlot: Int) {
        slots[selectedSlot] = player.name
    }

    fun isSlotTaken(index: Int): Boolean {
       return slots[index] == Player.X.name || slots[index] == Player.O.name
    }

    fun areAllSlotsTaken(): Boolean = slots.all { it == Player.X.name || it == Player.O.name }

    fun reset() {
        for (index in slots.indices) {
            slots[index] = "${index + 1}"
        }
    }
}

TicTacToeGame.kt

class TicTacToeGame {
    private var currentPlayer: Player = Player.X
    private var xScore = 0
    private var oScore = 0
    private val board = Board()
    private var isPlaying = true

    fun play() {
        board.show()

        while (isPlaying) {
            print("\n\n${currentPlayer.name}'s turn(1-9): ")
            var input: Int

            do {
                try {
                    input = readln().toInt()

                    if (board.isSlotTaken(input - 1)) print("Slot is occupied, try again(1 - 9): ")
                    else
                        break
                } catch (e: NumberFormatException) {
                    print("Unexpected character entered, try again (1 - 9): ")
                }
            } while (true)

            board.insertPlayerMove(currentPlayer, input - 1)
            println()
            board.show()

            when {
                board.isPlayerWinner(currentPlayer) -> {
                    println("\n\n${currentPlayer.name} won!")

                    updateScore(winner = currentPlayer)
                    showLeaderBoard()
                    checkIfPlayAgain()
                }

                board.areAllSlotsTaken() -> {
                    println("\n\nTie game!")
                    checkIfPlayAgain()
                }

                else -> {
                    currentPlayer = if (currentPlayer == Player.X) Player.O else Player.X
                }
            }
        }
    }

    private fun updateScore(winner: Player) {
        if (winner == Player.X) {
            xScore += 10
        } else {
            oScore += 10
        }
    }

    private fun showLeaderBoard() {
        println("----Game leaderboard----")
        println("Player ${Player.X.name}'s score: $xScore")
        println("Player ${Player.O.name}'s score: $oScore")
    }

    private fun checkIfPlayAgain() {
        print("\nPress \"r\" if you want to play again, any character to quit: ")
        val r = readln()
        if (r == "r") {
            println()
            board.reset()
            board.show()
        } else {
            println("Thanks for playing!!")
            isPlaying = false
        }
    }
}


fun main() {
    val game = TicTacToeGame()
    game.play()
}