diff --git a/src/main/java/GraphWithMapData.java b/src/main/java/GraphWithMapData.java
index 0e4c09b..8f9ab03 100644
--- a/src/main/java/GraphWithMapData.java
+++ b/src/main/java/GraphWithMapData.java
@@ -6,6 +6,7 @@ import java.util.Map;
 //Can't just write the graph, because I need the occupancy data too.
 //Makes most sense to serialize object and write that to a file.
 //Which means there's no reason to split map data and graph data up.
+//Custom vertex class means a lot of the map data can now be encoded in the graph itself
 public class GraphWithMapData implements java.io.Serializable {
 
     private String sourceFilename;