feat: 重構例句填空與例句重組功能

## 例句填空重大改進
- 實現真正的例句挖空功能，支援點擊輸入
- 添加例句圖片顯示，提供視覺化學習輔助
- 重新設計答案回饋為滿版左對齊布局
- 優化提示功能顯示詞彙定義而非字母提示
- 移除例句中文翻譯，專注於英文理解

## 例句重組功能增強
- 添加例句圖片顯示功能
- 保持與例句填空一致的視覺設計

## 其他優化
- 修復翻卡記憶標題置中問題
- 優化詞彙聽力模式，移除定義和翻譯干擾
- 統一所有測驗模式的標題和布局格式

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/app/learn/page.tsx

@@ -391,16 +391,34 @@ export default function LearnPage() {
                 <div className="card-front">
                   <div
                     ref={cardFrontRef}
-                    className="bg-white rounded-xl shadow-lg text-center cursor-pointer hover:shadow-xl transition-shadow"
+                    className="bg-white rounded-xl shadow-lg cursor-pointer hover:shadow-xl transition-shadow p-8"
                   >
-                    <h2 className="text-4xl font-bold text-gray-900 mb-6">
-                      {currentCard.word}
-                    </h2>
-                    <div className="flex items-center justify-center gap-3">
-                      <span className="text-lg text-gray-500">
-                        {currentCard.pronunciation}
+                    {/* Title and Instructions */}
+                    <div className="flex justify-between items-start mb-6">
+                      <h2 className="text-2xl font-bold text-gray-900">
+                        翻卡記憶
+                      </h2>
+                      <span className="bg-blue-100 text-blue-800 text-xs px-2 py-1 rounded-full">
+                        {currentCard.difficulty}
                       </span>
-                      <AudioPlayer text={currentCard.word} />
+                    </div>
+                    <p className="text-lg text-gray-700 mb-2 text-left">
+                      點擊卡片翻面，根據你對單字的熟悉程度進行自我評估：
+                    </p>
+
+                    {/* Word Display */}
+                    <div className="flex-1 flex items-center justify-center mt-6">
+                      <div className="bg-gray-50 rounded-lg p-8 w-full text-center">
+                        <h3 className="text-4xl font-bold text-gray-900 mb-6">
+                          {currentCard.word}
+                        </h3>
+                        <div className="flex items-center justify-center gap-3">
+                          <span className="text-lg text-gray-500">
+                            {currentCard.pronunciation}
+                          </span>
+                          <AudioPlayer text={currentCard.word} />
+                        </div>
+                      </div>
                     </div>
                   </div>
                 </div>
@@ -599,87 +617,124 @@ export default function LearnPage() {
                   {currentCard.difficulty}
                 </span>
               </div>
-              <p className="text-lg text-gray-700 mb-2 text-left">
-                請根據定義和翻譯，輸入對應的英文單字：
-              </p>
 
-              <div className="text-center mb-8">
-                <div className="bg-gray-50 rounded-lg p-6 mb-6">
-                  <p className="text-lg text-gray-700 mb-4">
-                    <strong>定義：</strong>{currentCard.definition}
-                  </p>
-                  <p className="text-lg text-gray-700">
-                    <strong>中文翻譯：</strong>{currentCard.translation}
-                  </p>
-                </div>
-                <p className="text-lg text-gray-700 mb-4">
-                  請輸入對應的英文單字：
-                </p>
-              </div>
-
-              <div className="max-w-md mx-auto">
-                <input
-                  type="text"
-                  value={fillAnswer}
-                  onChange={(e) => setFillAnswer(e.target.value)}
-                  onKeyDown={(e) => {
-                    if (e.key === 'Enter' && !showResult && fillAnswer.trim()) {
-                      handleFillAnswer()
-                    }
-                  }}
-                  placeholder="輸入英文單字..."
-                  disabled={showResult}
-                  className="w-full p-4 text-center text-xl border-2 border-gray-200 rounded-lg focus:border-blue-500 focus:outline-none disabled:bg-gray-100"
-                />
-
-                <div className="flex gap-2 mt-4">
-                  {!showResult && fillAnswer.trim() && (
-                    <button
-                      onClick={handleFillAnswer}
-                      className="flex-1 px-4 py-2 bg-primary text-white rounded-lg hover:bg-primary-dark transition-colors"
-                    >
-                      確認答案
-                    </button>
-                  )}
-                  <button
-                    onClick={() => setShowHint(!showHint)}
-                    className="px-4 py-2 bg-gray-500 text-white rounded-lg hover:bg-gray-600 transition-colors"
-                  >
-                    {showHint ? '隱藏提示' : '顯示提示'}
-                  </button>
-                </div>
-
-                {showHint && (
-                  <div className="mt-4 p-4 bg-yellow-50 border border-yellow-200 rounded-lg">
-                    <p className="text-yellow-800">
-                      <strong>提示：</strong>這個詞有 {currentCard.word.length} 個字母，
-                      開頭是 "{currentCard.word[0].toUpperCase()}"
-                    </p>
+              {/* Example Image */}
+              {currentCard.exampleImage && (
+                <div className="mb-6">
+                  <div className="bg-gray-50 rounded-lg p-4">
+                    <img
+                      src={currentCard.exampleImage}
+                      alt="Example illustration"
+                      className="w-full max-w-md mx-auto rounded-lg cursor-pointer"
+                      onClick={() => setModalImage(currentCard.exampleImage)}
+                    />
                   </div>
-                )}
+                </div>
+              )}
+            <p className="text-lg text-gray-700 mb-2 text-left">
+                請點擊例句中的空白處輸入正確的單字：
+              </p>
+              {/* Example Sentence with Blanks */}
+              <div className="mb-6">
+                <div className="bg-gray-50 rounded-lg p-6">
+                  <div className="text-lg text-gray-700 leading-relaxed">
+                    {currentCard.example.split(new RegExp(`(${currentCard.word})`, 'gi')).map((part, index) => {
+                      const isTargetWord = part.toLowerCase() === currentCard.word.toLowerCase();
+                      return isTargetWord ? (
+                        <span key={index} className="relative inline-block mx-1">
+                          <input
+                            type="text"
+                            value={fillAnswer}
+                            onChange={(e) => setFillAnswer(e.target.value)}
+                            onKeyDown={(e) => {
+                              if (e.key === 'Enter' && !showResult && fillAnswer.trim()) {
+                                handleFillAnswer()
+                              }
+                            }}
+                            placeholder=""
+                            disabled={showResult}
+                            className={`inline-block px-2 py-1 text-center bg-transparent focus:outline-none disabled:bg-gray-100 ${
+                              fillAnswer
+                                ? 'border-b-2 border-blue-500'
+                                : 'border-b-2 border-dashed border-gray-400 focus:border-blue-400 focus:border-solid'
+                            }`}
+                            style={{ width: `${Math.max(100, Math.max(currentCard.word.length * 12, fillAnswer.length * 12 + 20))}px` }}
+                          />
+                          {!fillAnswer && (
+                            <span
+                              className="absolute inset-0 flex items-center justify-center text-gray-400 pointer-events-none"
+                              style={{ paddingBottom: '8px' }}
+                            >
+                              ____
+                            </span>
+                          )}
+                        </span>
+                      ) : (
+                        <span key={index}>{part}</span>
+                      );
+                    })}
+                  </div>
+                </div>
               </div>
 
+              {/* Action Buttons */}
+              <div className="flex gap-3 mb-4">
+                {!showResult && fillAnswer.trim() && (
+                  <button
+                    onClick={handleFillAnswer}
+                    className="px-6 py-2 bg-primary text-white rounded-lg hover:bg-primary-dark transition-colors"
+                  >
+                    確認答案
+                  </button>
+                )}
+                <button
+                  onClick={() => setShowHint(!showHint)}
+                  className="px-6 py-2 bg-gray-500 text-white rounded-lg hover:bg-gray-600 transition-colors"
+                >
+                  {showHint ? '隱藏提示' : '顯示提示'}
+                </button>
+              </div>
+
+              {/* Hint Section */}
+              {showHint && (
+                <div className="mb-4 p-4 bg-yellow-50 border border-yellow-200 rounded-lg">
+                  <h4 className="font-semibold text-yellow-800 mb-2">詞彙定義：</h4>
+                  <p className="text-yellow-800">{currentCard.definition}</p>
+                </div>
+              )}
+
               {showResult && (
-                <div className={`mt-6 p-4 rounded-lg max-w-md mx-auto ${
+                <div className={`mt-6 p-6 rounded-lg w-full ${
                   fillAnswer.toLowerCase().trim() === currentCard.word.toLowerCase()
                     ? 'bg-green-50 border border-green-200'
                     : 'bg-red-50 border border-red-200'
                 }`}>
-                  <p className={`font-semibold text-center ${
+                  <p className={`font-semibold text-left text-xl mb-4 ${
                     fillAnswer.toLowerCase().trim() === currentCard.word.toLowerCase()
                       ? 'text-green-700'
                       : 'text-red-700'
                   }`}>
                     {fillAnswer.toLowerCase().trim() === currentCard.word.toLowerCase() ? '正確！' : '錯誤！'}
                   </p>
+
                   {fillAnswer.toLowerCase().trim() !== currentCard.word.toLowerCase() && (
-                    <p className="text-gray-700 mt-2 text-center">
-                      正確答案是：<strong>{currentCard.word}</strong>
-                    </p>
+                    <div className="mb-4">
+                      <p className="text-gray-700 text-left">
+                        正確答案是：<strong className="text-lg">{currentCard.word}</strong>
+                      </p>
+                    </div>
                   )}
-                  <div className="mt-4 text-center">
-                    <p className="text-gray-600 mb-2">發音：{currentCard.pronunciation}</p>
-                    <AudioPlayer text={currentCard.word} />
+
+                  <div className="space-y-3">
+                    <div className="text-left">
+                      <p className="text-gray-600">
+                        <span className="mx-2">{currentCard.pronunciation}</span>
+                        <AudioPlayer text={currentCard.word} />
+                      </p>
+                    </div>
+
+                    <div className="text-left">
+                    </div>
                   </div>
                 </div>
               )}
@@ -732,23 +787,15 @@ export default function LearnPage() {
                 請聽發音並選擇正確的英文單字：
               </p>
 
-              <div className="text-center mb-8">
-
-                <div className="bg-gray-50 rounded-lg p-6 mb-6">
-                  <p className="text-lg text-gray-700 mb-4">
-                    <strong>中文翻譯：</strong>{currentCard.translation}
-                  </p>
-                  <p className="text-lg text-gray-700">
-                    <strong>定義：</strong>{currentCard.definition}
-                  </p>
-                </div>
-                <p className="text-lg text-gray-700 mb-6">
-                  請聽發音並選擇正確的英文單字：
-                </p>
-                <div className="mb-8">
-                  <AudioPlayer
-                    text={currentCard.word}
-                  />
+              {/* Content Sections */}
+              <div className="space-y-4 mb-8">
+                {/* Audio */}
+                <div className="bg-gray-50 rounded-lg p-4">
+                  <h3 className="font-semibold text-gray-900 mb-2 text-left">發音</h3>
+                  <div className="flex items-center gap-3">
+                    <span className="text-gray-700">{currentCard.pronunciation}</span>
+                    <AudioPlayer text={currentCard.word} />
+                  </div>
                 </div>
               </div>
 
@@ -1009,12 +1056,26 @@ export default function LearnPage() {
                   {currentCard.difficulty}
                 </span>
               </div>
-              <p className="text-lg text-gray-700 mb-2 text-left">
+ 
+
+              {/* Example Image */}
+              {currentCard.exampleImage && (
+                <div className="mb-6">
+                  <div className="bg-gray-50 rounded-lg p-4">
+                    <img
+                      src={currentCard.exampleImage}
+                      alt="Example illustration"
+                      className="w-full max-w-md mx-auto rounded-lg cursor-pointer"
+                      onClick={() => setModalImage(currentCard.exampleImage)}
+                    />
+                  </div>
+                </div>
+              )}
+             <p className="text-lg text-gray-700 mb-2 text-left">
                 請將下方的單字重新排列成正確的句子：
               </p>
-
+              
               <div className="text-center mb-8">
-
                 <div className="bg-gray-50 rounded-lg p-6 mb-6">
                   <p className="text-lg text-gray-700 mb-4">
                     <strong>詞彙：</strong>{currentCard.word}
@@ -1023,7 +1084,6 @@ export default function LearnPage() {
                     <strong>翻譯：</strong>{currentCard.exampleTranslation}
                   </p>
                 </div>
-
               </div>
 
               <div className="mb-6">
@@ -1174,8 +1234,8 @@ export default function LearnPage() {
           height: 100%;
           display: flex;
           flex-direction: column;
-          justify-content: center;
-          align-items: center;
+          justify-content: flex-start;
+          align-items: stretch;
           padding: 2rem;
           box-sizing: border-box;
         }