diff --git a/src/geometry.rs b/src/geometry.rs
index 761ce35..b87aff4 100644
--- a/src/geometry.rs
+++ b/src/geometry.rs
@@ -73,6 +73,7 @@ impl PartialEq for Point {
     }
 }
 
+// Marker trait to indicate reflexivity of equality (not just transitivity & symmetry)
 impl Eq for Point {}
 
 impl Rectangle {