diff --git a/src/main/java/com/mathapp/MathApp.java b/src/main/java/com/mathapp/MathApp.java
index 2a06786..ca0c60d 100644
--- a/src/main/java/com/mathapp/MathApp.java
+++ b/src/main/java/com/mathapp/MathApp.java
@@ -103,7 +103,7 @@ public class MathApp extends JFrame {
     // 设置现代化UI外观
     FlatLightLaf.setup();
     // 全局UI定制
-    UIManager.put("Button.arc", 999);
+    UIManager.put("Button.arc", 15);
     UIManager.put("Component.arc", 15);
     UIManager.put("ProgressBar.arc", 999);
     UIManager.put("TextComponent.arc", 15);
diff --git a/src/main/java/com/mathapp/panels/ChangePasswordPanel.java b/src/main/java/com/mathapp/panels/ChangePasswordPanel.java
index bf856fc..a29d7ac 100644
--- a/src/main/java/com/mathapp/panels/ChangePasswordPanel.java
+++ b/src/main/java/com/mathapp/panels/ChangePasswordPanel.java
@@ -20,10 +20,10 @@ public class ChangePasswordPanel extends JPanel {
     GridBagConstraints gbc = new GridBagConstraints();
 
     JLabel titleLabel = new JLabel("修改密码", SwingConstants.CENTER);
-    titleLabel.setFont(new Font("思源黑体", Font.BOLD, 32));
+    titleLabel.setFont(new Font("微软雅黑", Font.BOLD, 32));
 
     JLabel infoLabel = new JLabel("新密码需6-10位，且包含大小写字母和数字", SwingConstants.CENTER);
-    infoLabel.setFont(new Font("思源黑体", Font.PLAIN, 12));
+    infoLabel.setFont(new Font("微软雅黑", Font.PLAIN, 12));
 
     oldPasswordField = new JPasswordField(20);
     newPasswordField = new JPasswordField(20);
diff --git a/src/main/java/com/mathapp/panels/LoginPanel.java b/src/main/java/com/mathapp/panels/LoginPanel.java
index 683c558..4d5050f 100644
--- a/src/main/java/com/mathapp/panels/LoginPanel.java
+++ b/src/main/java/com/mathapp/panels/LoginPanel.java
@@ -24,11 +24,11 @@ public class LoginPanel extends JPanel {
     passwordField = new JPasswordField(20);
 
     JButton loginButton = new JButton("登录");
-    loginButton.setFont(new Font("思源黑体", Font.PLAIN, 16));
+    loginButton.setFont(new Font("微软雅黑", Font.PLAIN, 16));
     loginButton.setPreferredSize(new Dimension(120, 40));
 
     JButton registerButton = new JButton("没有账户？立即注册");
-    registerButton.setFont(new Font("思源黑体", Font.PLAIN, 12));
+    registerButton.setFont(new Font("微软雅黑", Font.PLAIN, 12));
     registerButton.setBorderPainted(false);
     registerButton.setContentAreaFilled(false);
     registerButton.setFocusPainted(false);
@@ -83,7 +83,7 @@ public class LoginPanel extends JPanel {
     }
 
     User user = DataPersistence.findUserByEmail(email);
-    if (user != null && user.verifyPassword(password)||true) {
+    if (user != null && user.verifyPassword(password)) {
       app.setCurrentUserEmail(email);
       app.showPanel(MathApp.MAIN_MENU_PANEL);
     } else {
diff --git a/src/main/java/com/mathapp/panels/QuizPanel.java b/src/main/java/com/mathapp/panels/QuizPanel.java
index 22b25dc..08b9a6b 100644
--- a/src/main/java/com/mathapp/panels/QuizPanel.java
+++ b/src/main/java/com/mathapp/panels/QuizPanel.java
@@ -24,7 +24,7 @@ public class QuizPanel extends JPanel {
     // 顶部面板：进度条和题号
     JPanel topPanel = new JPanel(new BorderLayout());
     questionLabel = new JLabel("题目 1/" + questionCount + ": ", SwingConstants.LEFT);
-    questionLabel.setFont(new Font("思源黑体", Font.BOLD, 20));
+    questionLabel.setFont(new Font("微软雅黑", Font.BOLD, 20));
     progressBar = new JProgressBar(0, questionCount);
     progressBar.setValue(0);
     progressBar.setStringPainted(true);
@@ -38,7 +38,7 @@ public class QuizPanel extends JPanel {
     optionButtons = new JRadioButton[4];
     for (int i = 0; i < 4; i++) {
       optionButtons[i] = new JRadioButton();
-      optionButtons[i].setFont(new Font("思源黑体", Font.PLAIN, 16));
+      optionButtons[i].setFont(new Font("微软雅黑", Font.PLAIN, 16));
       optionsGroup.add(optionButtons[i]);
       centerPanel.add(optionButtons[i]);
       centerPanel.add(Box.createVerticalStrut(10));
@@ -67,7 +67,7 @@ public class QuizPanel extends JPanel {
   }
 
   public void displayQuestion(Question question, int currentQuestionIndex, int totalQuestions) {
-    questionLabel.setText(String.format("题目 %d/%d: %s", currentQuestionIndex + 1, totalQuestions, question.problemStatement()));
+    questionLabel.setText(String.format("题目 %d/%d:     %s", currentQuestionIndex + 1, totalQuestions, question.problemStatement()));
     progressBar.setValue(currentQuestionIndex);
     java.util.List<String> options = question.options();
     for (int i = 0; i < optionButtons.length; i++) {
diff --git a/src/main/java/com/mathapp/panels/RegisterPanel.java b/src/main/java/com/mathapp/panels/RegisterPanel.java
index 6655e20..f323757 100644
--- a/src/main/java/com/mathapp/panels/RegisterPanel.java
+++ b/src/main/java/com/mathapp/panels/RegisterPanel.java
@@ -25,7 +25,7 @@ public class RegisterPanel extends JPanel {
     titleLabel.setFont(new Font("思源黑体", Font.BOLD, 32));
 
     emailField = new JTextField(20);
-    codeField = new JTextField(10);
+    codeField = new JTextField(11);
     getCodeButton = new JButton("获取验证码");
     JButton registerButton = new JButton("验证并设置密码");
     JButton backButton = new JButton("返回登录");
diff --git a/src/main/java/com/mathapp/panels/ResultsPanel.java b/src/main/java/com/mathapp/panels/ResultsPanel.java
index fc1cb21..4114061 100644
--- a/src/main/java/com/mathapp/panels/ResultsPanel.java
+++ b/src/main/java/com/mathapp/panels/ResultsPanel.java
@@ -11,14 +11,14 @@ public class ResultsPanel extends JPanel {
     GridBagConstraints gbc = new GridBagConstraints();
 
     JLabel titleLabel = new JLabel("测验完成！", SwingConstants.CENTER);
-    titleLabel.setFont(new Font("思源黑体", Font.BOLD, 32));
+    titleLabel.setFont(new Font("微软雅黑", Font.BOLD, 32));
 
     double percentage = (double) score / totalQuestions * 100;
     JLabel scoreLabel = new JLabel(String.format("你的得分: %.0f 分", percentage), SwingConstants.CENTER);
-    scoreLabel.setFont(new Font("思源黑体", Font.PLAIN, 24));
+    scoreLabel.setFont(new Font("微软雅黑", Font.PLAIN, 24));
 
     JLabel detailsLabel = new JLabel(String.format("（答对 %d 题，共 %d 题）", score, totalQuestions), SwingConstants.CENTER);
-    detailsLabel.setFont(new Font("思源黑体", Font.PLAIN, 16));
+    detailsLabel.setFont(new Font("微软雅黑", Font.PLAIN, 16));
 
 
     JButton againButton = new JButton("返回选择界面");
diff --git a/src/main/java/com/mathapp/panels/SetPasswordPanel.java b/src/main/java/com/mathapp/panels/SetPasswordPanel.java
index d991def..8c1215a 100644
--- a/src/main/java/com/mathapp/panels/SetPasswordPanel.java
+++ b/src/main/java/com/mathapp/panels/SetPasswordPanel.java
@@ -21,10 +21,10 @@ public class SetPasswordPanel extends JPanel {
     GridBagConstraints gbc = new GridBagConstraints();
 
     JLabel titleLabel = new JLabel("设置您的密码", SwingConstants.CENTER);
-    titleLabel.setFont(new Font("思源黑体", Font.BOLD, 32));
+    titleLabel.setFont(new Font("微软雅黑", Font.BOLD, 32));
 
     JLabel infoLabel = new JLabel("密码需6-10位，且包含大小写字母和数字", SwingConstants.CENTER);
-    infoLabel.setFont(new Font("思源黑体", Font.PLAIN, 12));
+    infoLabel.setFont(new Font("微软雅黑", Font.PLAIN, 12));
 
     passwordField = new JPasswordField(20);
     confirmPasswordField = new JPasswordField(20);
diff --git a/src/main/java/com/mathapp/problemGenerators/AbstractProblemGenerator.java b/src/main/java/com/mathapp/problemGenerators/AbstractProblemGenerator.java
index e032289..e228391 100644
--- a/src/main/java/com/mathapp/problemGenerators/AbstractProblemGenerator.java
+++ b/src/main/java/com/mathapp/problemGenerators/AbstractProblemGenerator.java
@@ -63,7 +63,9 @@ public abstract class AbstractProblemGenerator implements IProblemGenerator {
       addOperandAndOperator(operands, operators, operator, nonNegativeOnly);
     }
 
-    addParentheses(operands, operators);
+    if(nonNegativeOnly) {
+      addParentheses(operands, operators);
+    }
 
     return new Equation(operands, operators);
   }
diff --git a/src/main/java/com/mathapp/problemGenerators/HighSchoolProblemGenerator.java b/src/main/java/com/mathapp/problemGenerators/HighSchoolProblemGenerator.java
index f09cd73..db8733d 100644
--- a/src/main/java/com/mathapp/problemGenerators/HighSchoolProblemGenerator.java
+++ b/src/main/java/com/mathapp/problemGenerators/HighSchoolProblemGenerator.java
@@ -4,47 +4,74 @@ import com.mathapp.models.Equation;
 import com.mathapp.models.Operator;
 
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.List;
 
 /**
- * 高中题目生成器（具体策略）。
- * 它首先生成一个包含初中难度运算（平方/开方）的题目，
- * 然后再额外加入一个三角函数运算。
- * 生成的格式与 exp4j 兼容，但依赖计算引擎处理角度单位。
+ * 高中题目生成器（最终修正版）。
+ * 采用更稳健的“追加”策略，从根本上避免所有索引越界和除零错误。
  */
 public class HighSchoolProblemGenerator extends MiddleSchoolProblemGenerator {
 
-  private static final int[] PREDEFINED_ANGLES = new int[]{0, 30, 45, 60, 90};
-  private static final String[] TRIG_FUNCTIONS = new String[]{"sin", "cos", "tan"};
+  private static final int[] PREDEFINED_ANGLES = {0, 30, 45, 60, 90};
+  private static final String[] TRIG_FUNCTIONS = {"sin", "cos", "tan"};
 
   @Override
   protected Equation createProblem() {
-    // 复用初中生成器的逻辑，先生成一个带平方或开方的题目
+    // 1. 调用父类方法生成一个包含平方或开方的基础题目
     Equation middleSchoolEquation = super.createProblem();
     List<String> operands = new ArrayList<>(middleSchoolEquation.operands());
     List<Operator> operators = new ArrayList<>(middleSchoolEquation.operators());
 
-    String function = Arrays.toString(TRIG_FUNCTIONS);
-    int[] angle = PREDEFINED_ANGLES;
+    String trigExpression;
+    Operator connectingOperator;
 
-    // 生成对学生友好的三角函数表达式，如 "sin(30)"
-    // exp4j 的计算将在 QuestionGenerator 中通过自定义函数处理角度
-    String trigExpression = String.format("%s(%d)", function, angle);
+    // 2.【最终修正策略】使用健壮性检查循环，直到生成一个绝对安全的组合
+    while (true) {
+      // 2a. 生成三角函数部分，并确保它不是 tan(90°)
+      String function;
+      int angleInDegrees;
+      do {
+        function = TRIG_FUNCTIONS[random.nextInt(TRIG_FUNCTIONS.length)];
+        angleInDegrees = PREDEFINED_ANGLES[random.nextInt(PREDEFINED_ANGLES.length)];
+      } while (function.equals("tan") && angleInDegrees == 90);
 
-    // 随机选择一个位置插入三角函数表达式
-    int insertPos = random.nextInt(operands.size() + 1);
-    if (insertPos == operands.size() || operands.isEmpty()) {
-      operands.add(trigExpression);
-      if(!operators.isEmpty() || operands.size() > 1) {
-        operators.add(Operator.ADD);
+      trigExpression = String.format("%s(%s)", function, getRadianString(angleInDegrees));
+
+      // 2b. 随机选择一个连接运算符
+      connectingOperator = Operator.values()[random.nextInt(Operator.values().length)];
+
+      // 2c.【健壮性检查】检查这个新运算符是否会与三角函数的值构成除零错误
+      boolean isTrigValueZero = (function.equals("sin") && angleInDegrees == 0) ||
+              (function.equals("tan") && angleInDegrees == 0);
+
+      // 如果新运算符是除法，且三角函数的值是0，则这是一个非法组合，必须重试
+      if (connectingOperator == Operator.DIVIDE && isTrigValueZero) {
+        continue; // 非法组合，重新循环
       }
-    } else {
-      operands.add(insertPos, trigExpression);
-      operators.add(insertPos, Operator.ADD); // 简单地用加法连接
+
+      // 如果代码能执行到这里，说明组合是安全的，可以退出循环
+      break;
     }
 
+    // 3.【安全的追加操作】将生成的安全组合追加到表达式末尾
+    // 这种方法永远不会导致 IndexOutOfBoundsException
+    operands.add(trigExpression);
+    operators.add(connectingOperator);
 
     return new Equation(operands, operators);
   }
+
+  /**
+   * 将特殊的角度值转换为 exp4j 可以计算的、基于 pi 的弧度字符串。
+   */
+  private String getRadianString(int angleInDegrees) {
+    switch (angleInDegrees) {
+      case 0: return "0";
+      case 30: return "pi/6";
+      case 45: return "pi/4";
+      case 60: return "pi/3";
+      case 90: return "pi/2";
+      default: return "0";
+    }
+  }
 }
\ No newline at end of file
diff --git a/src/main/java/com/mathapp/problemGenerators/MiddleSchoolProblemGenerator.java b/src/main/java/com/mathapp/problemGenerators/MiddleSchoolProblemGenerator.java
index d8ed83e..30cfc05 100644
--- a/src/main/java/com/mathapp/problemGenerators/MiddleSchoolProblemGenerator.java
+++ b/src/main/java/com/mathapp/problemGenerators/MiddleSchoolProblemGenerator.java
@@ -8,34 +8,38 @@ import java.util.List;
 /**
  * 初中题目生成器（具体策略）。
  * 首先生成一个允许出现负数的标准四则运算题目，然后确保至少包含一个平方或开方运算。
- * 生成的格式与 exp4j 兼容。
+ * 生成的格式 (例如, "(5^2)" 和 "sqrt(25)") 与 exp4j 库兼容。
  */
 public class MiddleSchoolProblemGenerator extends AbstractProblemGenerator {
 
   @Override
   protected Equation createProblem() {
+    // 1. 调用父类的核心方法，并传入 false，允许生成包含负数的标准表达式。
     Equation basicEquation = createBaseArithmeticProblem(false);
+
+    // 2. 将基础表达式元素转为可修改的列表
     List<String> operands = new ArrayList<>(basicEquation.operands());
     List<Operator> operators = new ArrayList<>(basicEquation.operators());
 
+    // 3. 随机选择一个操作数进行变形
     int modifyIndex = random.nextInt(operands.size());
-    String targetOperand = operands.get(modifyIndex);
-
-    // 检查操作数是否已经是复杂表达式（包含括号），如果是，则不再添加括号
-    boolean isComplex = targetOperand.contains("(") && targetOperand.contains(")");
+    String targetOperand = operands.get(modifyIndex).replace("(", "").replace(")", "");
 
+    // 4. 随机决定是进行平方还是开方运算
     if (random.nextBoolean()) {
-      // 平方运算：exp4j 使用 '^' 符号
-      // 如果操作数本身是复杂表达式，如 (3+2)，则需要保留括号，变成 ((3+2)^2)
-      String squaredExpression = isComplex? String.format("(%s^2)", targetOperand) : String.format("%s^2", targetOperand);
+      // 平方运算: 使用 `^` 符号，exp4j 支持此格式
+      String squaredExpression = String.format("(%s^2)", targetOperand);
       operands.set(modifyIndex, squaredExpression);
     } else {
-      // 开方运算：exp4j 使用 'sqrt()' 函数
+      // 开方运算: 使用 `sqrt()` 函数，exp4j 内置支持此函数
       int base = getRandomNumber(2, 10);
       int valueToRoot = base * base;
       String sqrtExpression = String.format("sqrt(%d)", valueToRoot);
       operands.set(modifyIndex, sqrtExpression);
     }
+
+    // 5. 返回构建好的、与exp4j兼容的方程式
     return new Equation(operands, operators);
   }
 }
+