diff --git a/assignments/PA4/semant.h b/assignments/PA4/semant.h
index 1d97e01..e8c6694 100644
--- a/assignments/PA4/semant.h
+++ b/assignments/PA4/semant.h
@@ -25,19 +25,23 @@ typedef ClassTable *ClassTableP;
 
 class ClassGraphNode {
 private:
+  // tree-shape relation maintainer
   ClassGraphNode* parent;
   std::vector<ClassGraphNode*> children;
+  // the `class__class` object for which it builds graph
   Class_ self;
+  // for cycle detection
   int mark = 0;
 
 public:
   // Note that, Class_ = Class__class*, itself is a ptr type, so just use it
   ClassGraphNode(Class_ self_class, ClassGraphNode* parent_class = nullptr) :
     parent(parent_class), self(self_class) { }
+  // Explicitly disable copy constructor
   ClassGraphNode(const ClassGraphNode&) = delete;
   ClassGraphNode& operator=(const ClassGraphNode) = delete;
+  // Long time no C++, god knows if the destructor works or not...
   ~ ClassGraphNode() {
-    // Long time no C++, god knows if the destructor works or not...
     while (!children.empty()) {
       auto child = children[children.size() - 1];
       children.pop_back();
@@ -112,9 +116,14 @@ private:
   int semant_errors;
   void install_basic_classes();
   ostream& error_stream;
+
+  // Root of the Inheritance Graph (hopefully it is a tree if the program is correct)
   ClassGraphNode* class_root;
-  std::map<Symbol, ClassGraphNode*> name_to_node;
+
   // again, the correctness of using ptr can be inferred from `Single Copy` of the symbol string
+  // Actually, we could use the provided symbol table instead of a stl map for this
+  //  anyways we don't need name shadowing here, I just save my effort
+  std::map<Symbol, ClassGraphNode*> name_to_node;
 
 public:
   ClassTable(Classes);