Simple CLI coin flip game in functional Scala.

Coin.scala

import scala.io.StdIn.readLine
import scala.util.Random
import scala.annotation.tailrec

case class GameState(nFlips: Int, nCorrect: Int)

object Coin {
    def prompt(): Unit = { print("(H) Heads, (T) Tails, (Q) End Game: ") }

    def update(g: GameState): Unit = { println(s"nFlips = ${g.nFlips}, nCorrect = ${g.nCorrect}\n") }

    def read(): String = readLine().trim.toUpperCase

    def flip(): String = { if (Random.nextFloat() < 0.5) "H" else "T" }

    @tailrec
    def mainLoop(g: GameState): GameState = {
        prompt()
        val input = read()
        input match {
            case "Q" => { g }
            case "H" | "T" => {
                val newState = GameState(g.nFlips + 1, g.nCorrect + (if (flip() == input) 1 else 0))
                update(newState)
                mainLoop(newState)
            }
            case _ => {
                println("Invalid option, try again\n")
                mainLoop(g)
            }
        }
    }

    def main(args: Array[String]): Unit = {
        val g = mainLoop(GameState(0, 0))
        println()
        println("Final Results:")
        update(g)
    }
}