diff --git a/LearnEnglish/LearnEnglish/Views/QuizViewController.swift b/LearnEnglish/LearnEnglish/Views/QuizViewController.swift
index b82b7b4..fe3d345 100644
--- a/LearnEnglish/LearnEnglish/Views/QuizViewController.swift
+++ b/LearnEnglish/LearnEnglish/Views/QuizViewController.swift
@@ -41,9 +41,18 @@ final class QuizViewController: UIViewController {
         questions.indices.contains(currentIndex) ? questions[currentIndex] : nil
     }
 
+    private var isUppercase: Bool
+
     init(config: QuizConfig) {
         self.config = config
-        self.questions = QuizGenerator.makeQuestions(mode: config.mode, words: config.words)
+        let uppercase = UserDefaults.standard.bool(forKey: "spelling_uppercase")
+        self.isUppercase = uppercase
+        let words = config.words.map { word in
+            let text = uppercase ? word.word.uppercased() : word.word.lowercased()
+            return Word(word: text, phonetic: word.phonetic, meaning: word.meaning,
+                        example: word.example, exampleMeaning: word.exampleMeaning)
+        }
+        self.questions = QuizGenerator.makeQuestions(mode: config.mode, words: words)
         super.init(nibName: nil, bundle: nil)
     }
 
@@ -59,6 +68,10 @@ final class QuizViewController: UIViewController {
         view.backgroundColor = .systemBackground
         title = config.mode.rawValue
         navigationItem.largeTitleDisplayMode = .never
+        navigationItem.leftBarButtonItem = UIBarButtonItem(
+            image: UIImage(systemName: "textformat"),
+            style: .plain, target: self, action: #selector(toggleCase))
+        updateCaseButton()
         buildLayout()
         showQuestion()
     }
@@ -331,7 +344,7 @@ final class QuizViewController: UIViewController {
     private func submitSpelling(_ typed: String, for question: QuizQuestion) {
         guard selectedOption == nil else { return }
         selectedOption = typed
-        let correct = typed == question.answer
+        let correct = typed.lowercased() == question.answer.lowercased()
         if !correct {
             wrongWords.append(question.word)
         }
@@ -344,7 +357,7 @@ final class QuizViewController: UIViewController {
     private func submitDictation(_ typed: String, for question: QuizQuestion) {
         guard selectedOption == nil else { return }
         selectedOption = typed
-        let correct = typed == question.answer
+        let correct = typed.lowercased() == question.answer.lowercased()
         if !correct {
             wrongWords.append(question.word)
         }
@@ -390,6 +403,17 @@ final class QuizViewController: UIViewController {
         }
     }
 
+    @objc private func toggleCase() {
+        isUppercase.toggle()
+        UserDefaults.standard.set(isUppercase, forKey: "spelling_uppercase")
+        updateCaseButton()
+        restart()
+    }
+
+    private func updateCaseButton() {
+        navigationItem.leftBarButtonItem?.tintColor = isUppercase ? Theme.Color.accent : .tertiaryLabel
+    }
+
     @objc private func speakCurrentWord() {
         guard let question = current else { return }
         speech.speak(question.word.word)
@@ -465,7 +489,12 @@ final class QuizViewController: UIViewController {
         countdownTimer?.invalidate()
         countdownLabel.isHidden = true
         view.subviews.compactMap { $0 as? QuizResultView }.forEach { $0.removeFromSuperview() }
-        questions = QuizGenerator.makeQuestions(mode: config.mode, words: config.words)
+        let words = config.words.map { word in
+            let text = isUppercase ? word.word.uppercased() : word.word.lowercased()
+            return Word(word: text, phonetic: word.phonetic, meaning: word.meaning,
+                        example: word.example, exampleMeaning: word.exampleMeaning)
+        }
+        questions = QuizGenerator.makeQuestions(mode: config.mode, words: words)
         currentIndex = 0
         wrongWords = []
         startDate = .now