diff --git a/sweet_geometry.c b/sweet_geometry.c
index 01ffa88..3436a07 100644
--- a/sweet_geometry.c
+++ b/sweet_geometry.c
@@ -98,9 +98,10 @@ face_free (struct face_item * root)
 struct item
 {
     struct item * next;
-    unsigned int a;
+
+    unsigned int a; // a, b = Key
     unsigned int b;
-    unsigned int id;
+    unsigned int id; // id = Value
 };
 
 #define MAP_SIZE    8192