Thought of posting my solution to the challenge in the Guess the Flag: Wrap up.

For resetting the game after 8 turns, I've decided to do it in the same alert and use other state variables to control the content of the alert.

import SwiftUI

struct ContentView: View {
    @State private var showingScore = false
    @State private var score = 0
    @State private var currentGame = 1
    @State private var scoreTitle = ""
    @State private var alertButton = ""
    @State private var scoreType = ""
    @State private var countries = ["Estonia", "France", "Germany", "Ireland", "Italy", "Nigeria", "Poland", "Russia", "Spain", "UK", "US"].shuffled()
    @State private var correctAnswer = Int.random(in: 0...2)

    private let gameNumber = 8

    var body: some View {
        ZStack {
            RadialGradient(stops: [
                .init(color: Color(red: 0.1, green: 0.2, blue: 0.45), location: 0.3),
                .init(color: Color(red: 0.76, green: 0.15, blue: 0.26), location: 0.3),
            ], center: .top, startRadius: 200, endRadius: 400)
            .ignoresSafeArea()

            VStack {

                Spacer()

                Text("Guess the Flag")
                    .font(.largeTitle.weight(.bold))
                    .foregroundColor(.white)

                VStack(spacing: 15) {
                    VStack {
                        Text("Tap the flag of")
                            .foregroundColor(.secondary)
                            .font(.subheadline.weight(.heavy))
                        Text(countries[correctAnswer])
                            .font(.largeTitle.weight(.semibold))
                    }

                    ForEach(0..<3) { number in
                        Button {
                            flagTapped(number)
                        } label: {
                            Image(countries[number])
                                .renderingMode(.original)
                                .clipShape(Capsule())
                                .shadow(radius: 5)
                        }

                    }
                }
                .frame(maxWidth: .infinity)
                .padding(.vertical, 20)
                .background(.regularMaterial)
                .clipShape(RoundedRectangle(cornerRadius: 20))

                Spacer()
                Spacer()

                Text("Score: \(score)")
                    .foregroundColor(.white)
                    .font(.title.bold())
                Text("Game \(currentGame)")
                    .foregroundColor(.white)
                    .font(.subheadline.weight(.bold))

                Spacer()
            }
            .padding()
            .alert(scoreTitle, isPresented: $showingScore) {
                Button(alertButton, action: askQuestion)
            } message: {
                Text("Your \(scoreType) is \(score)")
            }
        }
    }

    func askQuestion() {
        countries.shuffle()
        correctAnswer = Int.random(in: 0...2)
        currentGame = currentGame < gameNumber ? currentGame + 1 : 1
        if currentGame == 1 {
            score = 0
        }
    }

    func flagTapped(_ number: Int) {
        if number == correctAnswer {
            scoreTitle = "Correct 👍🏼"
            score += 1
        } else {
            scoreTitle = "Wrong 👎 That's the flag of \(countries[number])"
            score -= 1
        }

        alertButton = currentGame == gameNumber ? "Restart Game" : "Continue"
        scoreType = currentGame == gameNumber ? "final score" : "score"
        showingScore = true
    }

}