diff --git a/index.html b/index.html
index e3b90c6..fba934e 100644
--- a/index.html
+++ b/index.html
@@ -156,6 +156,10 @@ body { font-family: -apple-system, 'Segoe UI', sans-serif; background: var(--bg)
 .option.correct .radio::after { content: ''; width: 8px; height: 8px; border-radius: 50%; background: var(--green); }
 .option.wrong .radio { border-color: var(--red); }
 .option.wrong .radio::after { content: ''; width: 8px; height: 8px; border-radius: 50%; background: var(--red); }
+.option .checkbox { width: 18px; height: 18px; border: 2px solid var(--surface2); border-radius: 4px; flex-shrink: 0; display: flex; align-items: center; justify-content: center; font-size: 12px; color: white; transition: all 0.2s; }
+.option.selected .checkbox { border-color: var(--accent); background: var(--accent); }
+.option.correct .checkbox { border-color: var(--green); background: var(--green); }
+.option.wrong .checkbox { border-color: var(--red); background: var(--red); }
 
 /* Actions */
 .actions { display: flex; gap: 8px; flex-wrap: wrap; align-items: center; margin-top: 4px; }
@@ -508,19 +512,33 @@ function renderQuestionCard(q, i) {
 
   html += `</div>`;
 
-  // Options for single_choice
-  if (q.type === 'single_choice' && q.options) {
+  // Options for single_choice and multiple_choice
+  if ((q.type === 'single_choice' || q.type === 'multiple_choice') && q.options) {
+    const isMC = q.type === 'multiple_choice';
+    const selectedSet = isMC ? (state?.selected || []) : [];
     html += `<div class="options">`;
     for (const [letter, text] of Object.entries(q.options)) {
       let optClass = '';
       if (revealed) {
-        if (letter === q.answer) optClass = 'correct';
-        else if (state?.value === letter) optClass = 'wrong';
-      } else if (state?.value === letter) {
+        if (isMC) {
+          // multiple_choice: 'correct' = 答案里的正确项; 'wrong' = 用户误选的非正确项
+          const isCorrectAnswer = (q.answer || []).includes(letter);
+          const userSelected = selectedSet.includes(letter);
+          if (isCorrectAnswer) optClass = 'correct';
+          else if (userSelected) optClass = 'wrong';
+        } else {
+          if (letter === q.answer) optClass = 'correct';
+          else if (state?.value === letter) optClass = 'wrong';
+        }
+      } else if (isMC ? selectedSet.includes(letter) : state?.value === letter) {
         optClass = 'selected';
       }
-      html += `<div class="option ${optClass}" onclick="selectOption('${q.id}','${letter}')">
-        <div class="radio"></div>
+      const clickFn = isMC ? `toggleOption('${q.id}','${letter}')` : `selectOption('${q.id}','${letter}')`;
+      const marker = isMC
+        ? `<div class="checkbox"><span>${selectedSet.includes(letter) ? '✓' : ''}</span></div>`
+        : `<div class="radio"></div>`;
+      html += `<div class="option ${optClass}" onclick="${clickFn}">
+        ${marker}
         <span><strong>${letter}.</strong> ${escapeHtml(text)}</span>
       </div>`;
     }
@@ -562,6 +580,19 @@ function selectOption(qId, letter) {
   renderQuiz();
 }
 
+// Toggle an option for multiple_choice questions
+function toggleOption(qId, letter) {
+  const q = currentQuestions.find(x => x.id === qId);
+  if (!q || q.type !== 'multiple_choice' || answers[qId]?.revealed) return;
+  const cur = answers[qId];
+  const selected = cur?.selected ? [...cur.selected] : [];
+  const idx = selected.indexOf(letter);
+  if (idx >= 0) selected.splice(idx, 1);
+  else selected.push(letter);
+  answers[qId] = { value: selected.join(','), selected, correct: false, revealed: false };
+  renderQuiz();
+}
+
 function saveFill(qId) {
   const input = document.getElementById(`input-${qId}`);
   if (!input) return;
@@ -611,6 +642,12 @@ function revealAnswer(qId) {
 
   if (q.type === 'single_choice') {
     answers[qId].correct = answers[qId].value === q.answer;
+  } else if (q.type === 'multiple_choice') {
+    const userSel = (answers[qId].selected || []).slice().sort();
+    const correctSel = (q.answer || []).slice().sort();
+    answers[qId].correct = userSel.length === correctSel.length &&
+      userSel.every((x, i) => x === correctSel[i]);
+    // 让多选选项未选中状态也能正确显示
   }
   answers[qId].revealed = true;
   renderQuiz();
@@ -619,9 +656,14 @@ function revealAnswer(qId) {
 function showAllAnswers() {
   currentQuestions.forEach(q => {
     if (!answers[q.id]?.revealed) {
-      if (!answers[q.id]) answers[q.id] = { value: '', correct: false };
+      if (!answers[q.id]) answers[q.id] = { value: '', selected: [], correct: false };
       if (q.type === 'single_choice') {
         answers[q.id].correct = answers[q.id].value === q.answer;
+      } else if (q.type === 'multiple_choice') {
+        const userSel = (answers[q.id].selected || []).slice().sort();
+        const correctSel = (q.answer || []).slice().sort();
+        answers[q.id].correct = userSel.length === correctSel.length &&
+          userSel.every((x, i) => x === correctSel[i]);
       }
       answers[q.id].revealed = true;
     }
@@ -631,10 +673,15 @@ function showAllAnswers() {
 
 function submitAll() {
   currentQuestions.forEach(q => {
-    if (!answers[q.id]) answers[q.id] = { value: '', correct: false };
+    if (!answers[q.id]) answers[q.id] = { value: '', selected: [], correct: false };
     if (!answers[q.id].revealed) {
       if (q.type === 'single_choice') {
         answers[q.id].correct = answers[q.id].value === q.answer;
+      } else if (q.type === 'multiple_choice') {
+        const userSel = (answers[q.id].selected || []).slice().sort();
+        const correctSel = (q.answer || []).slice().sort();
+        answers[q.id].correct = userSel.length === correctSel.length &&
+          userSel.every((x, i) => x === correctSel[i]);
       } else if (q.type === 'fill_blank') {
         answers[q.id].correct = matchFillAnswer(answers[q.id].value, q.answer, q.answer_rule || 'any');
       }