diff --git a/src/com/mathlearning/model/QuestionGenerator.java b/src/com/mathlearning/model/QuestionGenerator.java
index afc3dc0..871427b 100644
--- a/src/com/mathlearning/model/QuestionGenerator.java
+++ b/src/com/mathlearning/model/QuestionGenerator.java
@@ -11,7 +11,7 @@ public class QuestionGenerator {
 
   public List<Question> generateQuestions(String level, int count) {
     List<Question> questions = new ArrayList<>();
-    Set<String> questionTexts = new HashSet<>(); // 防止重复题目
+    Set<String> questionTexts = new HashSet<>();
 
     for (int i = 0; i < count; i++) {
       Question question;
@@ -44,225 +44,275 @@ public class QuestionGenerator {
   }
 
   private Question generatePrimaryQuestion(int index) {
-    // 小学：操作数2-5个，确保结果不为负数
-    int operandCount = random.nextInt(4) + 2; // 2-5个操作数
+    int operandCount = random.nextInt(4) + 2;
     List<Integer> operands = new ArrayList<>();
     List<Character> operators = new ArrayList<>();
 
-    // 生成操作数 (1-100)
-    for (int i = 0; i < operandCount; i++) {
-      operands.add(random.nextInt(100) + 1);
-    }
-
-    // 生成运算符 (+, -, *, /)
-    for (int i = 0; i < operandCount - 1; i++) {
-      operators.add(getRandomOperation("+-*/"));
-    }
+    // 生成操作数和运算符，确保结果非负
+    generateSafePrimaryExpression(operands, operators, operandCount);
 
-    // 构建表达式并计算结果，确保不为负数
     String questionText;
     int result;
     int attempts = 0;
 
     do {
-      // 随机决定是否使用括号
       boolean useParentheses = random.nextBoolean() && operandCount >= 3;
-
       if (useParentheses) {
-        // 使用括号的表达式
         int parenPos = random.nextInt(operandCount - 1);
-        StringBuilder sb = new StringBuilder();
-
-        for (int i = 0; i < operandCount; i++) {
-          if (i == parenPos) {
-            sb.append("(");
-          }
-          sb.append(operands.get(i));
-          if (i == parenPos + 1) {
-            sb.append(")");
-          }
-          if (i < operandCount - 1) {
-            sb.append(" ").append(operators.get(i)).append(" ");
-          }
-        }
-
-        questionText = sb.toString();
-        result = evaluateExpressionWithParentheses(operands, operators, parenPos);
+        questionText = buildParenthesesExpression(operands, operators, parenPos);
+        result = evaluateWithParentheses(operands, operators, parenPos);
       } else {
-        // 不使用括号的表达式
-        StringBuilder sb = new StringBuilder();
-        for (int i = 0; i < operandCount; i++) {
-          sb.append(operands.get(i));
-          if (i < operandCount - 1) {
-            sb.append(" ").append(operators.get(i)).append(" ");
-          }
-        }
-
-        questionText = sb.toString();
+        questionText = buildSimpleExpression(operands, operators);
         result = evaluateSequential(operands, operators);
       }
 
       attempts++;
-      // 如果结果为负数，重新生成操作数和运算符
       if (result < 0) {
-        operands.clear();
-        operators.clear();
-        for (int i = 0; i < operandCount; i++) {
-          operands.add(random.nextInt(100) + 1);
-        }
-        for (int i = 0; i < operandCount - 1; i++) {
-          operators.add(getRandomOperation("+-*/"));
-        }
+        // 重新生成安全的表达式
+        generateSafePrimaryExpression(operands, operators, operandCount);
       }
     } while (result < 0 && attempts < 10);
 
     // 如果还是负数，强制使用加法
     if (result < 0) {
-      StringBuilder sb = new StringBuilder();
-      for (int i = 0; i < operandCount; i++) {
-        sb.append(operands.get(i));
-        if (i < operandCount - 1) {
-          sb.append(" + ");
-        }
+      for (int i = 0; i < operators.size(); i++) {
+        operators.set(i, '+');
       }
-      questionText = sb.toString();
-      result = operands.stream().mapToInt(Integer::intValue).sum();
+      questionText = buildSimpleExpression(operands, operators);
+      result = evaluateSequential(operands, operators);
     }
 
-    return generateOptions(questionText + " = ?", result, "小学");
+    return generateIntOptions(questionText + " = ?", result, "小学");
+  }
+
+  private void generateSafePrimaryExpression(List<Integer> operands, List<Character> operators, int operandCount) {
+    operands.clear();
+    operators.clear();
+
+    // 首先生成所有操作数
+    for (int i = 0; i < operandCount; i++) {
+      operands.add(random.nextInt(100) + 1);
+    }
+
+    // 然后生成安全的运算符序列
+    int currentValue = operands.get(0);
+    for (int i = 1; i < operandCount; i++) {
+      char op;
+      if (currentValue < operands.get(i)) {
+        // 如果当前值小于下一个操作数，避免减法导致负数
+        if (random.nextBoolean()) {
+          op = '+';
+          currentValue += operands.get(i);
+        } else {
+          op = (random.nextBoolean() && currentValue > 0) ? '*' : '+';
+          if (op == '*') currentValue *= operands.get(i);
+          else currentValue += operands.get(i);
+        }
+      } else {
+        // 可以安全使用减法
+        op = getRandomOperation("+-*/");
+        switch (op) {
+          case '+': currentValue += operands.get(i); break;
+          case '-': currentValue -= operands.get(i); break;
+          case '*': currentValue *= operands.get(i); break;
+          case '/':
+            if (operands.get(i) != 0) currentValue /= operands.get(i);
+            else currentValue += operands.get(i);
+            break;
+        }
+      }
+      operators.add(op);
+    }
   }
 
   private Question generateMiddleSchoolQuestion(int index) {
-    // 初中：操作数1-5个，至少包含平方或开根号
-    int operandCount = random.nextInt(5) + 1; // 1-5个操作数
-    boolean hasSquareOrSqrt = false;
-    String questionText;
-    int result;
-    int attempts = 0;
+    int type = random.nextInt(4);
+    MathExpression expression = new MathExpression();
+
+    switch (type) {
+      case 0:
+        expression = createSquareExpression();
+        break;
+      case 1:
+        expression = createSqrtExpression();
+        break;
+      case 2:
+        expression = createSquareProductExpression();
+        break;
+      case 3:
+        expression = createSquareDivisionExpression();
+        break;
+    }
 
-    do {
-      int type = random.nextInt(4);
-      switch (type) {
-        case 0:
-          // a² ± b × c
-          int a = random.nextInt(10) + 1; // 1-10的平方
-          int b = random.nextInt(100) + 1;
-          int c = random.nextInt(100) + 1;
-          char op = random.nextBoolean() ? '+' : '-';
-          questionText = a + "² " + op + " " + b + " × " + c;
-          result = (op == '+') ? (a * a + b * c) : (a * a - b * c);
-          hasSquareOrSqrt = true;
-          break;
+    // 确保初中题目结果非负
+    if (expression.result < 0) {
+      expression = createSquareExpression(); // 重新生成一个肯定为正的题目
+    }
 
-        case 1:
-          // √a ± b
-          int sqrtBase = findPerfectSquare(100); // 100以内的完全平方数
-          int sqrtVal = (int) Math.sqrt(sqrtBase);
-          int d = random.nextInt(100) + 1;
-          char op2 = random.nextBoolean() ? '+' : '-';
-          questionText = "√" + sqrtBase + " " + op2 + " " + d;
-          result = (op2 == '+') ? (sqrtVal + d) : (sqrtVal - d);
-          hasSquareOrSqrt = true;
-          break;
+    return generateIntOptions(expression.questionText + " = ?", expression.result, "初中");
+  }
 
-        case 2:
-          // a × b² ± c
-          int e = random.nextInt(100) + 1;
-          int f = random.nextInt(10) + 1;
-          int g = random.nextInt(100) + 1;
-          char op3 = random.nextBoolean() ? '+' : '-';
-          questionText = e + " × " + f + "² " + op3 + " " + g;
-          result = (op3 == '+') ? (e * f * f + g) : (e * f * f - g);
-          hasSquareOrSqrt = true;
-          break;
+  private MathExpression createSquareExpression() {
+    int a = random.nextInt(10) + 1;
+    int b = random.nextInt(100) + 1;
+    int c = random.nextInt(100) + 1;
+    // 只使用加法确保结果为正
+    char op = '+';
 
-        default:
-          // (a + b)² ÷ c
-          int h = random.nextInt(50) + 1;
-          int i = random.nextInt(50) + 1;
-          int j = random.nextInt(20) + 1;
-          questionText = "(" + h + " + " + i + ")² ÷ " + j;
-          result = (h + i) * (h + i) / j;
-          hasSquareOrSqrt = true;
-          break;
-      }
-      attempts++;
-    } while (!hasSquareOrSqrt && attempts < 10);
+    String questionText = a + "² " + op + " " + b + " × " + c;
+    int result = a * a + b * c;
 
-    return generateOptions(questionText + " = ?", result, "初中");
+    return new MathExpression(questionText, result);
+  }
+
+  private MathExpression createSqrtExpression() {
+    int sqrtBase = findPerfectSquare(100);
+    int sqrtVal = (int) Math.sqrt(sqrtBase);
+    int d = random.nextInt(100) + 1;
+    // 只使用加法确保结果为正
+    char op = '+';
+
+    String questionText = "√" + sqrtBase + " " + op + " " + d;
+    int result = sqrtVal + d;
+
+    return new MathExpression(questionText, result);
+  }
+
+  private MathExpression createSquareProductExpression() {
+    int e = random.nextInt(100) + 1;
+    int f = random.nextInt(10) + 1;
+    int g = random.nextInt(100) + 1;
+    // 只使用加法确保结果为正
+    char op = '+';
+
+    String questionText = e + " × " + f + "² " + op + " " + g;
+    int result = e * f * f + g;
+
+    return new MathExpression(questionText, result);
+  }
+
+  private MathExpression createSquareDivisionExpression() {
+    int h = random.nextInt(50) + 1;
+    int i = random.nextInt(50) + 1;
+    int sum = h + i;
+    int square = sum * sum;
+    int j = findDivisor(square);
+
+    String questionText = "(" + h + " + " + i + ")² ÷ " + j;
+    int result = square / j;
+
+    return new MathExpression(questionText, result);
   }
 
   private Question generateHighSchoolQuestion(int index) {
-    // 高中：操作数1-5个，至少包含sin,cos,tan
-    int operandCount = random.nextInt(5) + 1; // 1-5个操作数
-    boolean hasTrigFunction = false;
-    String questionText;
-    double result;
-    int attempts = 0;
+    int type = random.nextInt(4);
+    TrigExpression expression = new TrigExpression();
+
+    switch (type) {
+      case 0:
+        expression = createSinExpression();
+        break;
+      case 1:
+        expression = createCosExpression();
+        break;
+      case 2:
+        expression = createTanExpression();
+        break;
+      case 3:
+        expression = createSinCosExpression();
+        break;
+    }
 
-    // 常见角度值
-    double[] angles = {0, 30, 45, 60, 90, 120, 135, 150, 180};
-    String[] angleStrs = {"0°", "30°", "45°", "60°", "90°", "120°", "135°", "150°", "180°"};
-    double[] sinValues = {0, 0.5, Math.sqrt(2)/2, Math.sqrt(3)/2, 1, Math.sqrt(3)/2, Math.sqrt(2)/2, 0.5, 0};
-    double[] cosValues = {1, Math.sqrt(3)/2, Math.sqrt(2)/2, 0.5, 0, -0.5, -Math.sqrt(2)/2, -Math.sqrt(3)/2, -1};
-    double[] tanValues = {0, Math.sqrt(3)/3, 1, Math.sqrt(3), Double.POSITIVE_INFINITY, -Math.sqrt(3), -1, -Math.sqrt(3)/3, 0};
+    return generateDoubleOptions(expression.questionText + " = ?", expression.result, "高中");
+  }
 
-    do {
-      int type = random.nextInt(4);
-      switch (type) {
-        case 0:
-          // sin(a) ± b
-          int idx1 = random.nextInt(angles.length);
-          int b = random.nextInt(100) + 1;
-          char op = random.nextBoolean() ? '+' : '-';
-          questionText = "sin(" + angleStrs[idx1] + ") " + op + " " + b;
-          result = (op == '+') ? (sinValues[idx1] + b) : (sinValues[idx1] - b);
-          hasTrigFunction = true;
-          break;
+  private TrigExpression createSinExpression() {
+    String[] angles = {"0°", "30°", "45°", "60°", "90°"};
+    double[] sinValues = {0, 0.5, 0.71, 0.87, 1.0};
 
-        case 1:
-          // a × cos(b)
-          int a = random.nextInt(100) + 1;
-          int idx2 = random.nextInt(angles.length);
-          questionText = a + " × cos(" + angleStrs[idx2] + ")";
-          result = a * cosValues[idx2];
-          hasTrigFunction = true;
-          break;
+    int idx = random.nextInt(angles.length);
+    int b = random.nextInt(100) + 1;
+    // 只使用加法确保结果为正
+    char op = '+';
 
-        case 2:
-          // tan(a) ÷ b (避免tan(90°))
-          int idx3 = random.nextInt(angles.length);
-          while (angles[idx3] == 90) {
-            idx3 = random.nextInt(angles.length);
-          }
-          int c = random.nextInt(20) + 1;
-          questionText = "tan(" + angleStrs[idx3] + ") ÷ " + c;
-          result = tanValues[idx3] / c;
-          hasTrigFunction = true;
-          break;
+    String questionText = "sin(" + angles[idx] + ") " + op + " " + b;
+    double result = sinValues[idx] + b;
 
-        default:
-          // sin(a) × cos(b) ± c
-          int idx4 = random.nextInt(angles.length);
-          int idx5 = random.nextInt(angles.length);
-          int d = random.nextInt(100) + 1;
-          char op2 = random.nextBoolean() ? '+' : '-';
-          questionText = "sin(" + angleStrs[idx4] + ") × cos(" + angleStrs[idx5] + ") " + op2 + " " + d;
-          result = (op2 == '+') ? (sinValues[idx4] * cosValues[idx5] + d) : (sinValues[idx4] * cosValues[idx5] - d);
-          hasTrigFunction = true;
-          break;
-      }
-      attempts++;
-    } while (!hasTrigFunction && attempts < 10);
+    return new TrigExpression(questionText, result);
+  }
+
+  private TrigExpression createCosExpression() {
+    String[] angles = {"0°", "30°", "45°", "60°"};
+    double[] cosValues = {1.0, 0.87, 0.71, 0.5};
+
+    int idx = random.nextInt(angles.length);
+    int a = random.nextInt(100) + 1;
+
+    String questionText = a + " × cos(" + angles[idx] + ")";
+    double result = a * cosValues[idx];
 
-    return generateOptions(questionText + " = ?", result, "高中");
+    return new TrigExpression(questionText, result);
+  }
+
+  private TrigExpression createTanExpression() {
+    String[] angles = {"0°", "30°", "45°", "60°"};
+    double[] tanValues = {0, 0.58, 1.0, 1.73};
+
+    int idx = random.nextInt(angles.length);
+    int c = random.nextInt(20) + 1;
+
+    String questionText = "tan(" + angles[idx] + ") ÷ " + c;
+    double result = tanValues[idx] / c;
+
+    return new TrigExpression(questionText, result);
+  }
+
+  private TrigExpression createSinCosExpression() {
+    String[] angles = {"0°", "30°", "45°", "60°"};
+    double[] sinValues = {0, 0.5, 0.71, 0.87};
+    double[] cosValues = {1.0, 0.87, 0.71, 0.5};
+
+    int idx1 = random.nextInt(angles.length);
+    int idx2 = random.nextInt(angles.length);
+    int d = random.nextInt(100) + 1;
+    // 只使用加法确保结果为正
+    char op = '+';
+
+    String questionText = "sin(" + angles[idx1] + ") × cos(" + angles[idx2] + ") " + op + " " + d;
+    double product = sinValues[idx1] * cosValues[idx2];
+    double result = product + d;
+
+    return new TrigExpression(questionText, result);
   }
 
-  // 辅助方法
   private char getRandomOperation(String operations) {
     return operations.charAt(random.nextInt(operations.length()));
   }
 
+  private String buildSimpleExpression(List<Integer> operands, List<Character> operators) {
+    StringBuilder sb = new StringBuilder();
+    for (int i = 0; i < operands.size(); i++) {
+      sb.append(operands.get(i));
+      if (i < operands.size() - 1) {
+        sb.append(" ").append(operators.get(i)).append(" ");
+      }
+    }
+    return sb.toString();
+  }
+
+  private String buildParenthesesExpression(List<Integer> operands, List<Character> operators, int parenPos) {
+    StringBuilder sb = new StringBuilder();
+    for (int i = 0; i < operands.size(); i++) {
+      if (i == parenPos) sb.append("(");
+      sb.append(operands.get(i));
+      if (i == parenPos + 1) sb.append(")");
+      if (i < operands.size() - 1) {
+        sb.append(" ").append(operators.get(i)).append(" ");
+      }
+    }
+    return sb.toString();
+  }
+
   private int evaluateSequential(List<Integer> operands, List<Character> operators) {
     int result = operands.get(0);
     for (int i = 0; i < operators.size(); i++) {
@@ -271,11 +321,8 @@ public class QuestionGenerator {
     return result;
   }
 
-  private int evaluateExpressionWithParentheses(List<Integer> operands, List<Character> operators, int parenPos) {
-    // 先计算括号内的值
+  private int evaluateWithParentheses(List<Integer> operands, List<Character> operators, int parenPos) {
     int parenResult = calculate(operands.get(parenPos), operands.get(parenPos + 1), operators.get(parenPos));
-
-    // 构建新的操作数和运算符列表
     List<Integer> newOperands = new ArrayList<>();
     List<Character> newOperators = new ArrayList<>();
 
@@ -293,39 +340,43 @@ public class QuestionGenerator {
       }
     }
 
-    // 顺序计算剩余部分
     return evaluateSequential(newOperands, newOperators);
   }
 
   private int calculate(int a, int b, char op) {
     switch (op) {
       case '+': return a + b;
-      case '-':
-        // 确保减法结果不为负数
-        return Math.max(a - b, 0);
+      case '-': return Math.max(a - b, 0);
       case '*': return a * b;
-      case '/':
-        // 确保除法能整除且除数不为0
-        if (b == 0) return a;
-        return a / b;
+      case '/': return (b == 0) ? a : a / b;
       default: return a + b;
     }
   }
 
   private int findPerfectSquare(int max) {
-    // 找到小于等于max的完全平方数
-    List<Integer> perfectSquares = new ArrayList<>();
+    List<Integer> squares = new ArrayList<>();
     for (int i = 1; i * i <= max; i++) {
-      perfectSquares.add(i * i);
+      squares.add(i * i);
     }
-    return perfectSquares.get(random.nextInt(perfectSquares.size()));
+    return squares.get(random.nextInt(squares.size()));
   }
 
-  private Question generateOptions(String questionText, int answer, String level) {
+  private int findDivisor(int number) {
+    List<Integer> divisors = new ArrayList<>();
+    for (int i = 2; i <= Math.min(20, number); i++) {
+      if (number % i == 0) {
+        divisors.add(i);
+      }
+    }
+    return divisors.isEmpty() ? 1 : divisors.get(random.nextInt(divisors.size()));
+  }
+
+  private Question generateIntOptions(String questionText, int answer, String level) {
     String[] options = new String[4];
     Set<Integer> usedValues = new HashSet<>();
 
-    options[0] = String.valueOf(answer);
+    String correctAnswer = String.valueOf(answer);
+    options[0] = correctAnswer;
     usedValues.add(answer);
 
     for (int i = 1; i < 4; i++) {
@@ -335,27 +386,25 @@ public class QuestionGenerator {
         int range = Math.max(3, Math.abs(answer) / 5 + 1);
         int offset = random.nextInt(range * 2 + 1) - range;
         wrongAnswer = answer + offset;
-        // 确保错误答案不为负数
-        wrongAnswer = Math.max(wrongAnswer, 0);
+        wrongAnswer = Math.max(wrongAnswer, 0); // 确保错误答案也不为负
         attempts++;
-      } while (usedValues.contains(wrongAnswer) && attempts < 20);
-
-      if (usedValues.contains(wrongAnswer)) {
-        wrongAnswer = answer + i * 10 + 5;
-        wrongAnswer = Math.max(wrongAnswer, 0);
-      }
+        if (attempts > 20) {
+          wrongAnswer = answer + (i + 1) * 10 + 5;
+          break;
+        }
+      } while (wrongAnswer == answer || usedValues.contains(wrongAnswer));
 
       options[i] = String.valueOf(wrongAnswer);
       usedValues.add(wrongAnswer);
     }
 
     shuffleArray(options);
-    int correctIndex = findCorrectIndex(options, String.valueOf(answer));
+    int correctIndex = findCorrectIndex(options, correctAnswer);
 
     return new Question(questionText, options, correctIndex, level);
   }
 
-  private Question generateOptions(String questionText, double answer, String level) {
+  private Question generateDoubleOptions(String questionText, double answer, String level) {
     String[] options = new String[4];
     Set<String> usedValues = new HashSet<>();
 
@@ -367,11 +416,15 @@ public class QuestionGenerator {
       String wrongAnswer;
       int attempts = 0;
       do {
-        double offset = (random.nextDouble() - 0.5) * 2.0;
+        double offset = (random.nextDouble() - 0.5) * Math.max(1, Math.abs(answer) * 0.3);
         double wrongValue = answer + offset;
-        wrongAnswer = formatDouble(wrongValue);
+        wrongAnswer = formatDouble(Math.max(wrongValue, 0)); // 确保错误答案不为负
         attempts++;
-      } while (usedValues.contains(wrongAnswer) && attempts < 20);
+        if (attempts > 20) {
+          wrongAnswer = formatDouble(answer + (i + 1) * 2.5);
+          break;
+        }
+      } while (usedValues.contains(wrongAnswer) || wrongAnswer.equals(correctAnswer));
 
       options[i] = wrongAnswer;
       usedValues.add(wrongAnswer);
@@ -384,21 +437,15 @@ public class QuestionGenerator {
   }
 
   private String formatDouble(double value) {
-    if (Double.isInfinite(value)) {
-      return "∞";
-    }
-    if (Double.isNaN(value)) {
-      return "无解";
-    }
-    // 保留3位小数，去除多余的0
-    return String.format("%.3f", value).replaceAll("0*$", "").replaceAll("\\.$", "");
+    if (Double.isInfinite(value)) return "∞";
+    if (Double.isNaN(value)) return "无解";
+    if (Math.abs(value) < 0.001) return "0";
+    return String.format("%.2f", value).replaceAll("0*$", "").replaceAll("\\.$", "");
   }
 
   private int findCorrectIndex(String[] options, String correctAnswer) {
     for (int i = 0; i < options.length; i++) {
-      if (options[i].equals(correctAnswer)) {
-        return i;
-      }
+      if (options[i].equals(correctAnswer)) return i;
     }
     return 0;
   }
@@ -411,4 +458,29 @@ public class QuestionGenerator {
       array[i] = temp;
     }
   }
+
+  // 辅助类来存储题目和答案
+  private static class MathExpression {
+    String questionText;
+    int result;
+
+    MathExpression() {}
+
+    MathExpression(String questionText, int result) {
+      this.questionText = questionText;
+      this.result = result;
+    }
+  }
+
+  private static class TrigExpression {
+    String questionText;
+    double result;
+
+    TrigExpression() {}
+
+    TrigExpression(String questionText, double result) {
+      this.questionText = questionText;
+      this.result = result;
+    }
+  }
 }
\ No newline at end of file