This is the 'Education' part only - it's a mess already and so I did not go down the 'Entertainment' route.

100DaysOfSwitfUI - Day 35 - Edutainment App.swift

//
//  ContentView.swift
//  Edut(r)ainMe - Day35
//
//  Created by mbr73 on 04.10.22.
//

import SwiftUI

struct Question {
    
    var multiplier: Int
    var table: Int
    var answer : Int?
    
    init(_ multiplier: Int, _ table: Int) {
        self.multiplier = multiplier
        self.table = table
        self.answer = nil
    }
    
    var hasCorrectAnswer: Bool {
        answer ?? 0 == multiplier*table
    }
    
    var hasAnswer: Bool {
        answer != nil
    }
    
    var string: String {
        "\(multiplier) × \(table)"
    }
}

extension Question: Hashable {
    func hash(into hasher: inout Hasher) {
        hasher.combine(multiplier)
        hasher.combine(table)
    }
    
}



struct ContentView: View {

    enum GameState {
        case showingSettings
        case isRunning
        case showingResults
    }

    var gameStateTitle: String {
        switch gameState {
        case .showingSettings:
            return "Settings"
        case .isRunning:
            return "Question \(currentQuestion + 1)/\(numberOfQuestionsSelected)"
        case .showingResults:
            return "Results"
        }
    }
    
    @State private var gameState = GameState.showingSettings

    
    let numberOfQuestionsOptions = [5, 10, 20]
    @State private var numberOfQuestionsSelected = 5
    @State private var multiplicationUpTo = 2

    @State private var currentQuestion = 0
    @State private var correctAnswers = 0
    @State private var questions = Array<Question>()

    @FocusState private var answerTextFieldFocused: Bool

        
    func buildQuestions(upTo: Int, number: Int) {
        
        questions = Array<Question>()

        for i in 1...12 {
            for j in 1...upTo {
                questions.append(Question(i,j))
            }
        }
        
        questions.shuffle()
        questions.removeLast(upTo*12 - number)
    }

    
    var body: some View {
        NavigationView {
            List {
                switch gameState {
                case .showingSettings:
                    Section {
                        Stepper("Tables up to \(multiplicationUpTo)", value: $multiplicationUpTo, in: 2...12)
                        HStack {
                            Text("Questions")
                            Spacer()
                            Picker("Questions", selection: $numberOfQuestionsSelected) {
                                ForEach(numberOfQuestionsOptions, id: \.self) {
                                    Text("\($0)")
                                }
                            }
                            .pickerStyle(.segmented)
                        }                        
                    }   header: {
                        Text("Let /me EduT(r)ain U")
                    }   footer: {
                        Text("Multiplication tables to practice are 1 up to \(multiplicationUpTo) by asking \(numberOfQuestionsSelected) questions.")
                    }
                    
                    Section {
                        Button {
                            buildQuestions(upTo: multiplicationUpTo, number: numberOfQuestionsSelected)
                            currentQuestion = 0
                            correctAnswers = 0
                            answerTextFieldFocused = true
                            
                            withAnimation {
                                gameState = .isRunning
                            }
                            
                        } label: {
                            HStack {
                                Spacer()
                                Text("Go!")
                                Spacer()
                            }
                        }
                    }
                case .isRunning:
                                        
                    Section {
                        
                        HStack {
                            Text("What's") // Without the text the Spacer() causes an ugly gap!?!!
                            Spacer()
                            Text("\(questions[currentQuestion].string)")
                                .font(.largeTitle)
                            Spacer()
                        }
                        
                        TextField("Type in your answer", value: $questions[currentQuestion].answer, format: .number)
                            .keyboardType(.decimalPad)
                            .focused($answerTextFieldFocused)

                    } header: {
                        Text("Question from table \(questions[currentQuestion].table):")
                    }   footer: {
                        Text("Multiplication tables to practice are 1 up to \(multiplicationUpTo). This is a question from table \(questions[currentQuestion].table).")
                    }
                  
                case .showingResults:
                    Section {
                        ForEach(questions, id: \.self) { question in
                            HStack {
                                Text("\(question.string) = \(question.answer!)")
                                    .foregroundColor(question.hasCorrectAnswer ? .black : .red )
                                    //.font(.monospaced(.body)())
                                Spacer()
                                Text(question.hasCorrectAnswer ? "✅" : "❌")
                            }
                        }
                    } footer: {
                        Text("You had \(correctAnswers) out of \(numberOfQuestionsSelected) questions answered correctly.")
                    }
                    
                }
            }
            .navigationTitle(gameStateTitle)
            .toolbar {
                ToolbarItemGroup(placement: .navigationBarTrailing) {
                    if gameState == .isRunning {
                        Button("Abort") {
                            withAnimation {
                                gameState = .showingSettings
                            }
                        }
                    } else if gameState == .showingResults {
                        Button("Done") {
                            withAnimation {
                                gameState = .showingSettings
                            }
                        }
                        
                    }
                }
            }

        }.onSubmit {
            if gameState == .isRunning {
                   
                let question = questions[currentQuestion]
                
                if question.hasAnswer {

                    if question.hasCorrectAnswer
                    {   correctAnswers += 1
                    }

                    if currentQuestion+1 < questions.count {
                        currentQuestion += 1
                    }   else {
                        withAnimation {
                            gameState = .showingResults
                        }
                    }
                }
                
                answerTextFieldFocused = true
            }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}